Rhombohedral graphene multilayers host various broken-symmetry metallic phases as well as superconductors whose pairing mechanism and order parameter symmetry remain unsettled. Strikingly, experiments have revealed prominent superconducting regions in rhombohedral bilayer and trilayer graphene devices with proximity-induced Ising spin-orbit coupling. We propose that these superconductors descend from a common spin-canted normal state that spontaneously breaks a U(1) spin symmetry and thus supports soft magnon modes. In particular, we show that these soft modes can mediate pairing through interband scattering events that are symmetry forbidden in the absence of spin-orbit coupling, thus providing a promising explanation for spin-orbit-enabled pairing. Numerous other experimental observations—including nontrivial dependence of superconductivity on the spin-orbit coupling strength, in-plane magnetic fields, and Fermi surface structure—also naturally follow from our scenario.
", "doi": "10.1103/2ts4-cxhs", "issn": "2160-3308", "publisher": "American Physical Society", "publication": "Physical Review X", "publication_date": "2026-03-12", "series_number": "1", "volume": "16", "issue": "1", "pages": "011055" }, { "id": "authors:mqg5x-qsc02", "collection": "authors", "collection_id": "mqg5x-qsc02", "cite_using_url": "https://authors.library.caltech.edu/records/mqg5x-qsc02", "type": "article", "title": "Probing Defects with Quantum Simulator Snapshots", "author": [ { "family_name": "Sarma", "given_name": "Abhijat", "orcid": "0000-0002-0360-6222" }, { "family_name": "Myerson-Jain", "given_name": "Nayan" }, { "family_name": "Liu", "given_name": "Yue", "orcid": "0000-0002-5965-0644", "clpid": "Liu-Yue" }, { "family_name": "Manoj", "given_name": "Nandagopal", "orcid": "0009-0009-0780-7716", "clpid": "Manoj-Nandagopal" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Melko", "given_name": "Roger G.", "orcid": "0000-0002-5505-8176" }, { "family_name": "Xu", "given_name": "Cenke", "orcid": "0000-0002-2304-743X" } ], "abstract": "Snapshots—i.e., projective measurements of local degrees of freedom—are the most standard data taken in experiments on quantum simulators, usually to probe local physics. In this Letter we propose a simple protocol to experimentally probe physics of defects with these snapshots. Our protocol relies only on snapshots from the bulk system, without introducing the defect explicitly; as such, the physics of different kinds of defects can be probed using the same dataset. In particular, we demonstrate that, with snapshots of local spin configurations of, for example, the 1\u2062\ud835\udc51 Rydberg atom realization of the quantum Ising criticality, we can (1) extract the “defect entropy” and (2) access the continuous line of fixed points of effective defect conformal field theory.
", "doi": "10.1103/stk3-lm78", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2026-01-14", "series_number": "2", "volume": "136", "issue": "2", "pages": "020603" }, { "id": "authors:9e1zt-8xk89", "collection": "authors", "collection_id": "9e1zt-8xk89", "cite_using_url": "https://authors.library.caltech.edu/records/9e1zt-8xk89", "type": "article", "title": "Quantum Anomalous Hall Effects and Emergent SU(2) Hall Ferromagnets at Fractional Filling of Helical Trilayer Graphene", "author": [ { "family_name": "Niu", "given_name": "Sen", "orcid": "0000-0001-7935-8563" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Sheng", "given_name": "D.\u2009N.", "orcid": "0000-0003-1258-0826" }, { "family_name": "Peng", "given_name": "Yang", "orcid": "0000-0002-8868-2928", "clpid": "Peng-Yang" } ], "abstract": "Helical trilayer graphene realizes a versatile moiré system for exploring correlated topological states emerging from high Chern bands. Motivated by recent experimental observations of anomalous Hall effects at fractional fillings of magic-angle helical trilayers, we focus on the higher Chern number |\ud835\udc36band|=2 band and explore gapped many-body Hall states beyond the conventional Landau level paradigm. Through extensive exact diagonalization, we predict novel phases unattainable in a single |\ud835\udc36band| =1 band. At filling \ud835\udf08 =2/3 and \ud835\udf08 =1/3, a √3 ×√3 charge-ordered quantum Hall crystal and a Halperin fractional Chern insulator with Hall conductance |\ud835\udf0e\ud835\udc3b| =2\u2062\ud835\udc52²/3\u2062\u210e are predicted, respectively, indicating strong particle-hole asymmetry of the system. At half-filling \ud835\udf08 =1/2, an extensively degenerate pseudospin Hall ferromagnet featuring emergent SU(2) symmetry is found without the band being flat. Inspired by striking robustness of the ferromagnetic degeneracy, we develop a method to unveil and quantify the emergent symmetry via pseudospin operator construction in the presence of band dispersion and Coulomb interaction and demonstrate persistence of the SU(2) quantum numbers even far away from the chiral limit. Incorporating spin-valley degrees of freedom, we identify an optimal filling regime \ud835\udf08total =3 +\ud835\udf08 for realizing the above states. Notably, interflavor interactions renormalize the bandwidth and stabilize all the gapped phases even in realistic sublattice corrugation parameter regimes.
", "doi": "10.1103/rwd7-92z9", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2025-10-01", "series_number": "14", "volume": "135", "issue": "14", "pages": "146505" }, { "id": "authors:jr5bz-0zd08", "collection": "authors", "collection_id": "jr5bz-0zd08", "cite_using_url": "https://authors.library.caltech.edu/records/jr5bz-0zd08", "type": "article", "title": "Decoherence and Wave-Function Deformation of D\u2084 Non-Abelian Topological Order", "author": [ { "family_name": "Sala", "given_name": "Pablo", "orcid": "0000-0001-7512-505X", "clpid": "Sala-Pablo" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Verresen", "given_name": "Ruben", "orcid": "0000-0002-0385-7363" } ], "abstract": "The effect of decoherence on topological order (TO) has been most deeply understood for the toric code, the paragon of Abelian TOs. We show that certain non-Abelian TOs can be analyzed and understood to a similar degree, despite being significantly richer. We consider both wave-function deformations and quantum channels acting on \ud835\udc37\u2084 TO, which has recently been realized on a quantum processor. By identifying the corresponding local statistical mechanical spin or rotor model with \ud835\udc37\u2084 symmetry, we find a remarkable stability against proliferating non-Abelian anyons. This is shown by leveraging a reformulation in terms of the tractable O(2) loop model in the pure state case and \ud835\udc5b coupled O(2) loop models for Rényi-\ud835\udc5b quantities in the decoherence case—corresponding to worldlines of the proliferating anyon with quantum dimension 2. In particular, we find that the purity (\ud835\udc5b =2) remains deep in the \ud835\udc37\u2084 TO for any decoherence strength, while the \ud835\udc5b →∞ limit becomes critical upon maximally decohering a particular anyon type, similar to our wave-function deformation result. The information-theoretic threshold (\ud835\udc5b →1) appears to be controlled by a disordered version of these statistical mechanical models, akin to the toric code case although significantly more robust. We furthermore use Monte Carlo simulations to explore the phase diagrams when multiple anyon types proliferate at the same time, leading to a continued stability of the \ud835\udc37\u2084 TO in addition to critical phases with emergent U(1) symmetry. Instead of loop models, these are now described by net models corresponding to different anyon types coupled together according to fusion rules. This opens up the exploration of statistical mechanical models for decohered non-Abelian TO, which can inform optimal decoders and which in an ungauged formulation provides examples of non-Abelian strong-to-weak symmetry breaking.
", "doi": "10.1103/5ywn-6d3q", "issn": "2160-3308", "publisher": "American Physical Society", "publication": "Physical Review X", "publication_date": "2025-07-01", "series_number": "3", "volume": "15", "issue": "3", "pages": "031002" }, { "id": "authors:z46ar-n2708", "collection": "authors", "collection_id": "z46ar-n2708", "cite_using_url": "https://authors.library.caltech.edu/records/z46ar-n2708", "type": "article", "title": "Boundary transitions from a single round of measurements on gapless quantum states", "author": [ { "family_name": "Liu", "given_name": "Yue", "orcid": "0000-0002-5965-0644", "clpid": "Liu-Yue" }, { "family_name": "Murciano", "given_name": "Sara", "orcid": "0000-0002-1638-5692", "clpid": "Murciano-Sara" }, { "family_name": "Mross", "given_name": "David F.", "orcid": "0000-0002-6585-1469" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Measurements can qualitatively alter correlations and entanglement emerging in gapless quantum matter. We show how a single round of measurements on gapless quantum systems can, upon rotating the measurement basis, induce nontrivial transitions separating regimes displaying universal characteristics governed by distinct boundary conformal field theories. We develop the theory of such \"measurement-induced boundary transitions\" by investigating a gapless parent of the one-dimensional cluster state, obtained by appropriately symmetrizing a commuting projector Hamiltonian for the latter. Projective measurements on the cluster state are known to convert the wave function, after post-selection or decoding, into a long-range-ordered Greenberger-Horne-Zeilinger (GHZ) state. Similar measurements applied to the gapless parent (i) generate long-range order coexisting with power-law correlations when post-selecting for uniform outcomes, and (ii) yield power-law correlations distinct from those in the pre-measurement state upon decoding. In the post-selection scenario, rotating the measurement basis preserves long-range order up until a critical tilt angle marking a measurement-induced boundary transition to a power-law-ordered regime. Such a transition—which does not exist in the descendant cluster state—establishes new connections between measurement effects on many-body states and nontrivial renormalization-group flows. We extend our analysis to tricritical Ising and three-state Potts critical theories, which also display measurement-induced boundary transitions, and propose general criteria for their existence in other settings.
", "doi": "10.1103/l4b7-h5cd", "issn": "2643-1564", "publisher": "American Physical Society", "publication": "Physical Review Research", "publication_date": "2025-06-23", "series_number": "2", "volume": "7", "issue": "2", "pages": "023293" }, { "id": "authors:41qjx-r7e13", "collection": "authors", "collection_id": "41qjx-r7e13", "cite_using_url": "https://authors.library.caltech.edu/records/41qjx-r7e13", "type": "article", "title": "Superconductivity and spin canting in spin\u2013orbit-coupled trilayer graphene", "author": [ { "family_name": "Patterson", "given_name": "Caitlin L." }, { "family_name": "Sheekey", "given_name": "Owen I." }, { "family_name": "Arp", "given_name": "Trevor B." }, { "family_name": "Holleis", "given_name": "Ludwig F. W.", "orcid": "0000-0001-9718-2477" }, { "family_name": "Koh", "given_name": "Jin Ming", "orcid": "0000-0002-6130-5591", "clpid": "Koh-Jin-Ming" }, { "family_name": "Choi", "given_name": "Youngjoon", "orcid": "0000-0001-9783-5992" }, { "family_name": "Xie", "given_name": "Tian", "orcid": "0000-0002-6406-0403" }, { "family_name": "Xu", "given_name": "Siyuan" }, { "family_name": "Guo", "given_name": "Yi" }, { "family_name": "Stoyanov", "given_name": "Hari" }, { "family_name": "Redekop", "given_name": "Evgeny" }, { "family_name": "Zhang", "given_name": "Canxun" }, { "family_name": "Babikyan", "given_name": "Grigory" }, { "family_name": "Gong", "given_name": "David" }, { "family_name": "Zhou", "given_name": "Haoxin" }, { "family_name": "Cheng", "given_name": "Xiang" }, { "family_name": "Taniguchi", "given_name": "Takashi", "orcid": "0000-0002-1467-3105" }, { "family_name": "Watanabe", "given_name": "Kenji", "orcid": "0000-0003-3701-8119" }, { "family_name": "Huber", "given_name": "Martin E.", "orcid": "0000-0002-7638-902X" }, { "family_name": "Jin", "given_name": "Chenhao", "orcid": "0000-0002-5965-7475" }, { "family_name": "Lantagne-Hurtubise", "given_name": "\u00c9tienne", "orcid": "0000-0003-0417-6452", "clpid": "Lantagne-Hurtubise-\u00c9tienne" }, { "family_name": "Alicea", "given_name": "Jason F.", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Young", "given_name": "Andrea F.", "orcid": "0000-0001-5954-8028" } ], "abstract": "Graphene and transition metal dichalcogenide flat-band systems show similar phase diagrams, replete with magnetic1,2,3,4,5 and superconducting6,7,8,9,10,11 phases. An abiding question has been whether magnetic ordering competes with superconductivity or facilitates pairing. For example, recent studies of Bernal bilayer graphene in the presence of enhanced spin–orbit coupling show a substantial increase in the observed domain and critical temperature Tc of superconducting states12,13,14; however, the mechanism for this enhancement remains unknown. Here we show that introducing spin–orbit coupling in rhombohedral trilayer graphene (RTG) by substrate proximity effect generates new superconducting pockets for both electron and hole doping, with maximal Tc ≈ 300 mK, which is three times larger than in RTG encapsulated by hexagonal boron nitride. Using local magnetometry, we show that superconductivity straddles a transition between a spin-canted state with a finite in-plane magnetic moment and a state with complete spin–valley locking. This transition is reproduced in our Hartree–Fock calculations, in which this transition is driven by the competition between spin–orbit coupling and the carrier-density-tuned Hund’s interaction. Our experiment suggests that the enhancement of superconductivity by spin–orbit coupling is driven by a quantitative change in the canting angle rather than a change in the ground state symmetry. These results align with a recently proposed mechanism for the enhancement of superconductivity15, in which fluctuations in the spin-canting order contribute to the pairing interaction.
", "doi": "10.1038/s41586-025-08863-w", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2025-05-15" }, { "id": "authors:mpxyv-1cy14", "collection": "authors", "collection_id": "mpxyv-1cy14", "cite_using_url": "https://authors.library.caltech.edu/records/mpxyv-1cy14", "type": "article", "title": "Quantum Geometric Kohn-Luttinger Superconductivity", "author": [ { "family_name": "Shavit", "given_name": "Gal", "orcid": "0000-0003-1792-9249", "clpid": "Shavit-Gal" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Coulomb repulsion can, counterintuitively, mediate Cooper pairing via the Kohn-Luttinger mechanism. However, it is commonly believed that observability of the effect requires special circumstances, e.g., vicinity of the Fermi level to Van Hove singularities, significant lattice-induced band distortions, or nontrivial Fermi surface topologies. Here, we establish that quantum geometric properties of the constituent electrons can dramatically promote pairing from repulsion via dependence of screening on the quantum metric. We demonstrate quantum-geometry-enhanced superconductivity in two microscopic models with tunable quantum geometry, highlighting the crucial roles of quantum metric anisotropy and inhomogeneity. Our analysis provides an experimentally accessible figure of merit for the importance of quantum geometry to inducing unconventional superconductivity, indicating its relevance to graphene multilayers.
", "doi": "10.1103/physrevlett.134.176001", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2025-05-02", "series_number": "17", "volume": "134", "issue": "17", "pages": "176001" }, { "id": "authors:pkp7h-5je03", "collection": "authors", "collection_id": "pkp7h-5je03", "cite_using_url": "https://authors.library.caltech.edu/records/pkp7h-5je03", "type": "article", "title": "Symmetry-broken metallic orders in spin-orbit-coupled Bernal bilayer graphene", "author": [ { "family_name": "Koh", "given_name": "Jin Ming", "orcid": "0000-0002-6130-5591", "clpid": "Koh-Jin-Ming" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Lantagne-Hurtubise", "given_name": "\u00c9tienne", "orcid": "0000-0003-0417-6452", "clpid": "Lantagne-Hurtubise-\u00c9tienne" } ], "abstract": "We explore Bernal bilayer graphene in the presence of long-range Coulomb interactions, short-range Hund's coupling, and proximity-induced Ising spin-orbit coupling using self-consistent Hartree-Fock simulations. We show that the interplay between these three ingredients produces an intricate phase diagram comprising a multitude of symmetry-broken metallic states tunable via doping and applied displacement field. In particular, we find intervalley coherent and spin-canted ground states that may hold the key to understanding spin-orbit-enabled superconductivity observed in this platform. We also investigate various phase transitions where a continuous U\u2061(1) symmetry is broken to ascertain the possible role of critical fluctuations on pairing.
", "doi": "10.1103/physrevb.110.245118", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2024-12-09", "series_number": "24", "volume": "110", "issue": "24", "pages": "245118" }, { "id": "authors:nd7ws-fpe76", "collection": "authors", "collection_id": "nd7ws-fpe76", "cite_using_url": "https://authors.library.caltech.edu/records/nd7ws-fpe76", "type": "article", "title": "Quantum Criticality Under Imperfect Teleportation", "author": [ { "family_name": "Sala", "given_name": "Pablo", "orcid": "0000-0001-7512-505X", "clpid": "Sala-Pablo" }, { "family_name": "Murciano", "given_name": "Sara", "orcid": "0000-0002-1638-5692", "clpid": "Murciano-Sara" }, { "family_name": "Liu", "given_name": "Yue", "orcid": "0000-0002-5965-0644", "clpid": "Liu-Yue" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Entanglement, measurement, and classical communication together enable teleportation of quantum states between distant parties, in principle, with perfect fidelity. To what extent do correlations and entanglement of a many-body wave function transfer under imperfect teleportation protocols? We address this question for the case of an imperfectly teleported quantum critical wave function, focusing on the ground state of a critical Ising chain. We demonstrate that imperfections, e.g., in the entangling gate adopted for a given protocol, effectively manifest as weak measurements acting on the otherwise pristinely teleported critical state. Armed with this perspective, we leverage and further develop the theory of measurement-altered quantum criticality to quantify the resilience of critical-state teleportation. We identify classes of teleportation protocols for which imperfection (i) preserves both the universal long-range entanglement and correlations of the original quantum critical state, (ii) weakly modifies these quantities away from their universal values, and (iii) obliterates long-range entanglement altogether while preserving power-law correlations, albeit with a new set of exponents. We also show that mixed states describing the average over a series of sequential imperfect teleportation events retain pristine power-law correlations due to a “built-in” decoding algorithm, though their entanglement structure measured by the negativity depends on errors similarly to individual protocol runs. These results may allow one to design teleportation protocols that optimize against errors—highlighting a potential practical application of measurement-altered criticality.
", "doi": "10.1103/prxquantum.5.030307", "issn": "2691-3399", "publisher": "American Physical Society", "publication": "PRX Quantum", "publication_date": "2024-07", "series_number": "3", "volume": "5", "issue": "3", "pages": "030307" }, { "id": "authors:ffdyp-7ka47", "collection": "authors", "collection_id": "ffdyp-7ka47", "cite_using_url": "https://authors.library.caltech.edu/records/ffdyp-7ka47", "type": "article", "title": "Correlated phases in spin-orbit-coupled rhombohedral trilayer graphene", "author": [ { "family_name": "Koh", "given_name": "Jin Ming", "orcid": "0000-0002-6130-5591", "clpid": "Koh-Jin-Ming" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Lantagne-Hurtubise", "given_name": "\u00c9tienne", "orcid": "0000-0003-0417-6452", "clpid": "Lantagne-Hurtubise-\u00c9tienne" } ], "abstract": "Recent experiments indicate that crystalline graphene multilayers exhibit much of the richness of their twisted counterparts, including cascades of symmetry-broken states and unconventional superconductivity. Interfacing Bernal bilayer graphene with a WSe\u2082 monolayer was shown to dramatically enhance superconductivity—suggesting that proximity-induced spin-orbit coupling plays a key role in promoting Cooper pairing. Motivated by this observation, we study the phase diagram of spin-orbit-coupled rhombohedral trilayer graphene via self-consistent Hartree-Fock simulations, elucidating the interplay between displacement field effects, long-range Coulomb repulsion, short-range (Hund's) interactions, and substrate-induced Ising spin-orbit coupling. In addition to generalized Stoner ferromagnets, we find various flavors of intervalley coherent ground states distinguished by their transformation properties under electronic time reversal, C\u2083 rotations, and an effective antiunitary symmetry. We pay particular attention to broken-symmetry phases that yield Fermi surfaces compatible with zero-momentum Cooper pairing, identifying promising candidate orders that may support spin-orbit-enhanced superconductivity.
", "doi": "10.1103/physrevb.109.035113", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2024-01-15", "series_number": "3", "volume": "109", "issue": "3", "pages": "035113" }, { "id": "authors:1fj0h-xbc90", "collection": "authors", "collection_id": "1fj0h-xbc90", "cite_using_url": "https://authors.library.caltech.edu/records/1fj0h-xbc90", "type": "article", "title": "Edge states of two-dimensional time-reversal invariant topological superconductors with strong interactions and disorder: A view from the lattice", "author": [ { "family_name": "Son", "given_name": "Jun Ho", "orcid": "0000-0002-7368-7005", "clpid": "Son-Jun-Ho" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Motrunich", "given_name": "Olexei I.", "orcid": "0000-0001-8031-0022", "clpid": "Motrunich-Olexei" } ], "abstract": "Two-dimensional time-reversal-invariant topological superconductors host helical Majorana fermions at their boundary. We study the fate of these edge states under the combined influence of strong interactions and disorder, using the effective one-dimensional (1D) lattice model for the edge introduced by Jones and Metlitski [Phys. Rev. B 104, 245130 (2021)]. We specifically develop a strong-disorder renormalization-group analysis of the lattice model and identify a regime in which time-reversal is broken spontaneously, creating random magnetic domains; Majorana fermions localize to domain walls and form an infinite-randomness fixed point, identical to that appearing in the random transverse-field Ising model. While this infinite-randomness fixed point describes a fine-tuned critical point in a purely 1D system, in our edge context there is no obvious time-reversal-preserving perturbation that destabilizes the fixed point. Our analysis thus suggests that the infinite-randomness fixed point emerges as a stable phase on the edge of two-dimensional topological superconductors when strong disorder and interactions are present.
", "doi": "10.1103/physrevb.109.035138", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2024-01-15", "series_number": "3", "volume": "109", "issue": "3", "pages": "035138" }, { "id": "authors:07zqt-kcp68", "collection": "authors", "collection_id": "07zqt-kcp68", "cite_using_url": "https://authors.library.caltech.edu/records/07zqt-kcp68", "type": "article", "title": "Imaging inter-valley coherent order in magic-angle twisted trilayer graphene", "author": [ { "family_name": "Kim", "given_name": "Hyunjin", "orcid": "0000-0001-9886-0487", "clpid": "Kim-Hyunjin" }, { "family_name": "Choi", "given_name": "Youngjoon", "orcid": "0000-0001-9783-5992", "clpid": "Choi-Youngjoon" }, { "family_name": "Lantagne-Hurtubise", "given_name": "\u00c9tienne", "orcid": "0000-0003-0417-6452", "clpid": "Lantagne-Hurtubise-\u00c9tienne" }, { "family_name": "Lewandowski", "given_name": "Cyprian", "orcid": "0000-0002-6944-9805", "clpid": "Lewandowski-Cyprian" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Kong", "given_name": "Lingyuan", "orcid": "0000-0002-0012-8341", "clpid": "Kong-Lingyuan" }, { "family_name": "Zhou", "given_name": "Haoxin", "orcid": "0000-0003-1235-0035", "clpid": "Zhou-Haoxin" }, { "family_name": "Baum", "given_name": "Eli", "orcid": "0000-0002-4550-7417", "clpid": "Baum-Eli" }, { "family_name": "Zhang", "given_name": "Yiran", "orcid": "0000-0002-8477-0074", "clpid": "Zhang-Yiran" }, { "family_name": "Holleis", "given_name": "Ludwig", "orcid": "0000-0001-9718-2477", "clpid": "Holleis-Ludwig" }, { "family_name": "Watanabe", "given_name": "Kenji", "orcid": "0000-0003-3701-8119", "clpid": "Watanabe-Kenji" }, { "family_name": "Taniguchi", "given_name": "Takashi", "orcid": "0000-0002-1467-3105", "clpid": "Taniguchi-Takashi" }, { "family_name": "Young", "given_name": "Andrea F.", "clpid": "Young-Andrea-F" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" } ], "abstract": "Magic-angle twisted trilayer graphene (MATTG) exhibits a range of strongly correlated electronic phases that spontaneously break its underlying symmetries1,2. Here we investigate the correlated phases of MATTG using scanning tunnelling microscopy and identify marked signatures of interaction-driven spatial symmetry breaking. In low-strain samples, over a filling range of about two to three electrons or holes per moir\u00e9 unit cell, we observe atomic-scale reconstruction of the graphene lattice that accompanies a correlated gap in the tunnelling spectrum. This short-scale restructuring appears as a Kekul\u00e9 supercell\u2014implying spontaneous inter-valley coherence between electrons\u2014and persists in a wide range of magnetic fields and temperatures that coincide with the development of the gap. Large-scale maps covering several moir\u00e9 unit cells further reveal a slow evolution of the Kekul\u00e9 pattern, indicating that atomic-scale reconstruction coexists with translation symmetry breaking at a much longer moir\u00e9 scale. We use auto-correlation and Fourier analyses to extract the intrinsic periodicity of these phases and find that they are consistent with the theoretically proposed incommensurate Kekul\u00e9 spiral order3,4. Moreover, we find that the wavelength characterizing moir\u00e9-scale modulations monotonically decreases with hole doping away from half-filling of the bands and depends weakly on the magnetic field. Our results provide essential insights into the nature of the correlated phases of MATTG in the presence of strain and indicate that superconductivity can emerge from an inter-valley coherent parent state.
", "doi": "10.1038/s41586-023-06663-8", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2023-11-30", "volume": "623", "pages": "942-948" }, { "id": "authors:4s2kj-mvx44", "collection": "authors", "collection_id": "4s2kj-mvx44", "cite_using_url": "https://authors.library.caltech.edu/records/4s2kj-mvx44", "type": "article", "title": "Assembling Kitaev honeycomb spin liquids from arrays of one-dimensional symmetry-protected topological phases", "author": [ { "family_name": "Liu", "given_name": "Yue", "orcid": "0000-0002-5965-0644", "clpid": "Liu-Yue" }, { "family_name": "Tantivasadakarn", "given_name": "Nathanan", "orcid": "0000-0001-5295-2124", "clpid": "Tantivasadakarn-Nathanan" }, { "family_name": "Slagle", "given_name": "Kevin", "orcid": "0000-0002-8036-3447", "clpid": "Slagle-Kevin" }, { "family_name": "Mross", "given_name": "David F.", "orcid": "0000-0002-6585-1469", "clpid": "Mross-David-F" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "The Kitaev honeycomb model, which is exactly solvable by virtue of an extensive number of conserved quantities, supports a gapless quantum spin liquid phase as well as gapped descendants relevant for fault-tolerant quantum computation. We show that the anomalous edge modes of one-dimensional (1D) cluster-state-like symmetry-protected topological (SPT) phases provide natural building blocks for a variant of the Kitaev model that enjoys only a subextensive number of conserved quantities. The symmetry of our variant allows a single additional nearest-neighbor perturbation, corresponding to an anisotropic version of the \u0393 term studied in the context of Kitaev materials. We determine the phase diagram of the model using exact diagonalization. Additionally, we use the density matrix renormalization group to show that the underlying 1D SPT building blocks can emerge from a ladder Hamiltonian exhibiting only two-spin interactions supplemented by a Zeeman field. Our approach may provide a pathway toward realizing Kitaev honeycomb spin liquids in spin-orbit-coupled Mott insulators.
", "doi": "10.1103/physrevb.108.184406", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2023-11-08", "series_number": "18", "volume": "108", "issue": "18", "pages": "184406" }, { "id": "authors:e8bce-b9w69", "collection": "authors", "collection_id": "e8bce-b9w69", "cite_using_url": "https://authors.library.caltech.edu/records/e8bce-b9w69", "type": "article", "title": "Gate-Defined Topological Josephson Junctions in Bernal Bilayer Graphene", "author": [ { "family_name": "Xie", "given_name": "Ying-Ming", "orcid": "0000-0002-2902-4896", "clpid": "Xie-Ying-Ming" }, { "family_name": "Lantagne-Hurtubise", "given_name": "\u00c9tienne", "orcid": "0000-0003-0417-6452", "clpid": "Lantagne-Hurtubise-\u00c9tienne" }, { "family_name": "Young", "given_name": "Andrea F.", "clpid": "Young-Andrea-F" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Recent experiments on Bernal bilayer graphene (BLG) deposited on monolayer WSe\u2082 revealed robust, ultraclean superconductivity coexisting with sizable induced spin-orbit coupling. Here, we propose BLG/WSe\u2082 as a platform to engineer gate-defined planar topological Josephson junctions, where the normal and superconducting regions descend from a common material. More precisely, we show that if superconductivity in BLG/WSe\u2082 is gapped and emerges from a parent state with intervalley coherence, then Majorana zero-energy modes can form in the barrier region upon applying weak in-plane magnetic fields. Our results spotlight a potential pathway for \"internally engineered\" topological superconductivity that minimizes detrimental disorder and orbital-magnetic-field effects.
", "doi": "10.1103/physrevlett.131.146601", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2023-10-06", "series_number": "14", "volume": "131", "issue": "14", "pages": "146601" }, { "id": "authors:6cbg3-bxg60", "collection": "authors", "collection_id": "6cbg3-bxg60", "cite_using_url": "https://authors.library.caltech.edu/records/6cbg3-bxg60", "type": "article", "title": "Measurement-Altered Ising Quantum Criticality", "author": [ { "family_name": "Murciano", "given_name": "Sara", "orcid": "0000-0002-1638-5692", "clpid": "Murciano-Sara" }, { "family_name": "Sala", "given_name": "Pablo", "orcid": "0000-0001-7512-505X", "clpid": "Sala-Pablo" }, { "family_name": "Liu", "given_name": "Yue", "orcid": "0000-0002-5965-0644", "clpid": "Liu-Yue" }, { "family_name": "Mong", "given_name": "Roger S.\u2009K.", "orcid": "0009-0000-7182-5681", "clpid": "Mong-Roger-S-K" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Quantum critical systems constitute appealing platforms for exploring novel measurement-induced phenomena due to their innate sensitivity to perturbations. We study the impact of measurements on paradigmatic Ising quantum-critical chains using an explicit protocol, whereby correlated ancillae are entangled with the critical chain and then projectively measured. Using a perturbative analytic framework supported by extensive numerical simulations, we demonstrate that measurements can qualitatively alter critical correlations in a manner dependent on the choice of entangling gate, ancilla measurement basis, measurement outcome, and nature of ancilla correlations. We further show that measurement-altered Ising criticality can be pursued surprisingly efficiently in experiments featuring of order 100 qubits by postselecting for high-probability measurement outcomes or, in certain cases, by averaging observables separately over measurement outcomes residing in distinct symmetry sectors. Our framework naturally adapts to more exotic quantum-critical points and highlights opportunities for realization in noisy intermediate-scale quantum hardware and in Rydberg arrays.
", "doi": "10.1103/physrevx.13.041042", "issn": "2160-3308", "publisher": "American Physical Society", "publication": "Physical Review X", "publication_date": "2023-10", "series_number": "4", "volume": "13", "issue": "4", "pages": "041042" }, { "id": "authors:yz6kc-3m611", "collection": "authors", "collection_id": "yz6kc-3m611", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230223-726426000.4", "type": "article", "title": "Enhanced superconductivity in spin\u2013orbit proximitized bilayer graphene", "author": [ { "family_name": "Zhang", "given_name": "Yiran", "orcid": "0000-0002-8477-0074", "clpid": "Zhang-Yiran" }, { "family_name": "Polski", "given_name": "Robert", "orcid": "0000-0003-0887-8099", "clpid": "Polski-Robert-M" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Lantagne-Hurtubise", "given_name": "\u00c9tienne", "orcid": "0000-0003-0417-6452", "clpid": "Lantagne-Hurtubise-\u00c9tienne" }, { "family_name": "Lewandowski", "given_name": "Cyprian", "orcid": "0000-0002-6944-9805", "clpid": "Lewandowski-Cyprian" }, { "family_name": "Zhou", "given_name": "Haoxin", "orcid": "0000-0003-1235-0035", "clpid": "Zhou-Haoxin" }, { "family_name": "Watanabe", "given_name": "Kenji", "orcid": "0000-0003-3701-8119", "clpid": "Watanabe-Kenji" }, { "family_name": "Taniguchi", "given_name": "Takashi", "orcid": "0000-0002-1467-3105", "clpid": "Taniguchi-Takashi" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" } ], "abstract": "In the presence of a large perpendicular electric field, Bernal-stacked bilayer graphene (BLG) features several broken-symmetry metallic phases as well as magnetic-field-induced superconductivity1. The superconducting state is quite fragile, however, appearing only in a narrow window of density and with a maximum critical temperature T\ua700\u2009\u2248\u200930\u2009mK. Here we show that placing monolayer tungsten diselenide (WSe\u2082) on BLG promotes Cooper pairing to an extraordinary degree: superconductivity appears at zero magnetic field, exhibits an order of magnitude enhancement in T\ua700 and occurs over a density range that is wider by a factor of eight. By mapping quantum oscillations in BLG\u2013WSe\u2082 as a function of electric field and doping, we establish that superconductivity emerges throughout a region for which the normal state is polarized, with two out of four spin-valley flavours predominantly populated. In-plane magnetic field measurements further reveal that superconductivity in BLG\u2013WSe\u2082 can exhibit striking dependence of the critical field on doping, with the Chandrasekhar\u2013Clogston (Pauli) limit roughly obeyed on one end of the superconducting dome, yet sharply violated on the other. Moreover, the superconductivity arises only for perpendicular electric fields that push BLG hole wavefunctions towards WSe\u2082, indicating that proximity-induced (Ising) spin\u2013orbit coupling plays a key role in stabilizing the pairing. Our results pave the way for engineering robust, highly tunable and ultra-clean graphene-based superconductors.", "doi": "10.1038/s41586-022-05446-x", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2023-01-12", "series_number": "7943", "volume": "613", "issue": "7943", "pages": "268-273" }, { "id": "authors:879kf-nd488", "collection": "authors", "collection_id": "879kf-nd488", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230523-599406900.1", "type": "article", "title": "Andreev reflection spectroscopy in strongly paired superconductors", "author": [ { "family_name": "Lewandowski", "given_name": "Cyprian", "orcid": "0000-0002-6944-9805", "clpid": "Lewandowski-Cyprian" }, { "family_name": "Lantagne-Hurtubise", "given_name": "\u00c9tienne", "orcid": "0000-0003-0417-6452", "clpid": "Lantagne-Hurtubise-\u00c9tienne" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-Stevan" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Motivated by recent experiments on low-carrier-density superconductors, including twisted multilayer graphene, we study signatures of the BCS-to-BEC evolution in Andreev reflection spectroscopy. We establish that in a standard quantum point contact geometry, Andreev reflection in a BEC superconductor is unable to mediate a zero-bias conductance beyond e\u00b2/h per lead channel. This bound is shown to result from a mapping that links the subgap conductance of BCS and BEC superconductors. We then demonstrate that sharp signatures of BEC superconductivity, including perfect Andreev reflection, can be recovered by tunneling through a suitably designed potential well. We propose various tunneling spectroscopy setups to experimentally probe this recovery.", "doi": "10.1103/physrevb.107.l020502", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2023-01-01", "series_number": "2", "volume": "107", "issue": "2", "pages": "Art. No. L020502" }, { "id": "authors:26v0a-8t069", "collection": "authors", "collection_id": "26v0a-8t069", "cite_using_url": "https://authors.library.caltech.edu/records/26v0a-8t069", "type": "article", "title": "Vortex-enabled Andreev processes in quantum Hall\u2013superconductor hybrids", "author": [ { "family_name": "Tang", "given_name": "Yuchen", "clpid": "Tang-Yuchen" }, { "family_name": "Knapp", "given_name": "Christina", "orcid": "0000-0002-5982-8107", "clpid": "Knapp-Christina" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Quantum Hall–superconductor heterostructures provide possible platforms for intrinsically fault-tolerant quantum computing. Motivated by several recent experiments that successfully integrated these phases, we investigate transport through a proximitized integer quantum Hall edge—paying particular attention to the impact of vortices in the superconductor. By examining the downstream conductance, we identify regimes in which subgap vortex levels mediate Andreev processes that would otherwise be frozen out in a vortex-free setup. Moreover, we show that at finite temperature, and in the limit of a large number of vortices, the downstream conductance can average to zero, indicating that the superconductor effectively behaves like a normal contact. Our results highlight the importance of considering vortices when using transport measurements to study superconducting correlations in quantum Hall–superconductor hybrids.
", "doi": "10.1103/physrevb.106.245411", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2022-12-15", "series_number": "24", "volume": "106", "issue": "24", "pages": "245411" }, { "id": "authors:202s5-wxx58", "collection": "authors", "collection_id": "202s5-wxx58", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221215-427737300.1", "type": "article", "title": "Promotion of superconductivity in magic-angle graphene multilayers", "author": [ { "family_name": "Zhang", "given_name": "Yiran", "orcid": "0000-0002-8477-0074", "clpid": "Zhang-Yiran" }, { "family_name": "Polski", "given_name": "Robert", "orcid": "0000-0003-0887-8099", "clpid": "Polski-Robert-M" }, { "family_name": "Lewandowski", "given_name": "Cyprian", "orcid": "0000-0002-6944-9805", "clpid": "Lewandowski-Cyprian" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Peng", "given_name": "Yang", "orcid": "0000-0002-8868-2928", "clpid": "Peng-Yang" }, { "family_name": "Choi", "given_name": "Youngjoon", "orcid": "0000-0001-9783-5992", "clpid": "Choi-Youngjoon" }, { "family_name": "Kim", "given_name": "Hyunjin", "orcid": "0000-0001-9886-0487", "clpid": "Kim-Hyunjin" }, { "family_name": "Watanabe", "given_name": "Kenji", "orcid": "0000-0003-3701-8119", "clpid": "Watanabe-Kenji" }, { "family_name": "Taniguchi", "given_name": "Takashi", "orcid": "0000-0002-1467-3105", "clpid": "Taniguchi-Takashi" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "von Oppen", "given_name": "Felix", "orcid": "0000-0002-2537-7256", "clpid": "von-Oppen-Felix" }, { "family_name": "Refael", "given_name": "Gil", "clpid": "Refael-G" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" } ], "abstract": "Graphene moir\u00e9 superlattices show an abundance of correlated insulating, topological, and superconducting phases. Whereas the origins of strong correlations and nontrivial topology can be directly linked to flat bands, the nature of superconductivity remains enigmatic. We demonstrate that magic-angle devices made of twisted tri-, quadri-, and pentalayer graphene placed on monolayer tungsten diselenide exhibit flavor polarization and superconductivity. We also observe insulating states in the tril- and quadrilayer arising at finite electric displacement fields. As the number of layers increases, superconductivity emerges over an enhanced filling-factor range, and in the pentalayer it extends well beyond the filling of four electrons per moir\u00e9 unit cell. Our results highlight the role of the interplay between flat and more dispersive bands in extending superconducting regions in graphene moir\u00e9 superlattices.", "doi": "10.1126/science.abn8585", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2022-09-30", "series_number": "6614", "volume": "377", "issue": "6614", "pages": "1538-1543" }, { "id": "authors:7bhnp-r9z60", "collection": "authors", "collection_id": "7bhnp-r9z60", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221031-575177800.11", "type": "article", "title": "Quantum spin liquids bootstrapped from Ising criticality in Rydberg arrays", "author": [ { "family_name": "Slagle", "given_name": "Kevin", "orcid": "0000-0002-8036-3447", "clpid": "Slagle-Kevin" }, { "family_name": "Liu", "given_name": "Yue", "orcid": "0000-0002-5965-0644", "clpid": "Liu-Yue" }, { "family_name": "Aasen", "given_name": "David", "orcid": "0000-0002-6552-488X", "clpid": "Aasen-David" }, { "family_name": "Pichler", "given_name": "Hannes", "orcid": "0000-0003-2144-536X", "clpid": "Pichler-Hannes" }, { "family_name": "Mong", "given_name": "Roger S. K.", "clpid": "Mong-Roger-S-K" }, { "family_name": "Chen", "given_name": "Xie", "orcid": "0000-0003-2215-2497", "clpid": "Chen-Xie" }, { "family_name": "Endres", "given_name": "Manuel", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Arrays of Rydberg atoms constitute a highly tunable, strongly interacting venue for the pursuit of exotic states of matter. We develop a strategy for accessing a family of fractionalized phases known as quantum spin liquids in two-dimensional Rydberg arrays. We specifically use effective field theory methods to study arrays assembled from Rydberg chains tuned to an Ising phase transition that famously hosts emergent fermions propagating within each chain. This highly entangled starting point allows us to naturally access spin liquids familiar from Kitaev's honeycomb model \u2014 albeit from an entirely different framework. In particular, we argue that finite-range repulsive Rydberg interactions, which frustrate nearby symmetry-breaking orders, can enable coherent propagation of emergent fermions between the chains in which they were born. Delocalization of emergent fermions across the full two-dimensional Rydberg array yields a gapless \u2124\u2082 spin liquid with a single massless Dirac cone. Here, the Rydberg occupation numbers exhibit universal power-law correlations that provide a straightforward experimental diagnostic of this phase. We further show that explicitly breaking symmetries perturbs the gapless spin liquid into gapped, topologically ordered descendants: Breaking lattice symmetries generates toric-code topological order, whereas introducing Floquet-mediated chirality generates non-Abelian Ising topological order. In the toric-code phase, we analytically construct microscopic incarnations of non-Abelian defects, which can be created and transported by dynamically controlling the atom positions in the array. Our work suggests that appropriately tuned Rydberg arrays provide a cold-atoms counterpart of solid-state \"Kitaev materials\" and, more generally, it spotlights a different angle for pursuing experimental platforms for Abelian and non-Abelian fractionalization.", "doi": "10.1103/physrevb.106.115122", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2022-09-15", "series_number": "11", "volume": "106", "issue": "11", "pages": "Art. No. 115122" }, { "id": "authors:5a1tw-xf975", "collection": "authors", "collection_id": "5a1tw-xf975", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-192424755", "type": "monograph", "title": "Vortex-enabled Andreev processes in quantum Hall-superconductor hybrids", "author": [ { "family_name": "Tang", "given_name": "Yuchen", "clpid": "Tang-Yuchen" }, { "family_name": "Knapp", "given_name": "Christina", "orcid": "0000-0002-5982-8107", "clpid": "Knapp-Christina" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Quantum Hall-superconductor heterostructures provide possible platforms for intrinsically fault-tolerant quantum computing. Motivated by several recent experiments that successfully integrated these phases, we investigate transport through a proximitized integer quantum Hall edge--paying particular attention to the impact of vortices in the superconductor. By examining the downstream conductance, we identify regimes in which sub-gap vortex levels mediate Andreev processes that would otherwise be frozen out in a vortex-free setup. Moreover, we show that at finite temperature, and in the limit of a large number of vortices, the downstream conductance can average to zero, indicating that the superconductor effectively behaves like a normal contact. Our results highlight the importance of considering vortices when using transport measurements to study superconducting correlations in quantum Hall-superconductor hybrids.", "doi": "10.48550/arXiv.2207.10687", "publisher": "arXiv", "publication_date": "2022-07-21" }, { "id": "authors:7btgy-p9d44", "collection": "authors", "collection_id": "7btgy-p9d44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-183023896", "type": "monograph", "title": "Andreev reflection spectroscopy in strongly paired superconductors", "author": [ { "family_name": "Lewandowski", "given_name": "Cyprian", "orcid": "0000-0002-6944-9805", "clpid": "Lewandowski-Cyprian" }, { "family_name": "Lantagne-Hurtubise", "given_name": "\u00c9tienne", "orcid": "0000-0003-0417-6452", "clpid": "Lantagne-Hurtubise-\u00c9tienne" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Motivated by recent experiments on low-carrier-density superconductors, including twisted multilayer graphene, we study signatures of the BCS to BEC evolution in Andreev reflection spectroscopy. We establish that in a standard quantum point contact geometry, Andreev reflection in a BEC superconductor is unable to mediate a zero-bias conductance beyond e\u00b2/h per lead channel. This bound is shown to result from a duality that links the sub-gap conductance of BCS and BEC superconductors. We then demonstrate that sharp signatures of BEC superconductivity, including perfect Andreev reflection, can be recovered by tunneling through a suitably designed potential well. We propose various tunneling spectroscopy setups to experimentally probe this recovery.", "doi": "10.48550/arXiv.2207.09494", "publisher": "arXiv", "publication_date": "2022-07-19" }, { "id": "authors:ngx9m-4wn04", "collection": "authors", "collection_id": "ngx9m-4wn04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211214-190046323", "type": "article", "title": "Dynamical Anyon Generation in Kitaev Honeycomb Non-Abelian Spin Liquids", "author": [ { "family_name": "Liu", "given_name": "Yue", "orcid": "0000-0002-5965-0644", "clpid": "Liu-Yue" }, { "family_name": "Slagle", "given_name": "Kevin", "orcid": "0000-0002-8036-3447", "clpid": "Slagle-Kevin" }, { "family_name": "Burch", "given_name": "Kenneth S.", "orcid": "0000-0002-7541-0245", "clpid": "Burch-Kenneth-S" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Relativistic Mott insulators known as \"Kitaev materials\" potentially realize spin liquids hosting non-Abelian anyons. Motivated by fault-tolerant quantum-computing applications in this setting, we introduce a dynamical anyon-generation protocol that exploits universal edge physics. The setup features holes in the spin liquid, which define energetically cheap locations for non-Abelian anyons, connected by a narrow bridge that can be tuned between spin liquid and topologically trivial phases. We show that modulating the bridge from trivial to spin liquid over intermediate time scales\u2014quantified by analytics and extensive simulations\u2014deposits non-Abelian anyons into the holes with O(1) probability. The required bridge manipulations can be implemented by integrating the Kitaev material into magnetic tunnel junction arrays that engender locally tunable exchange fields. Combined with existing readout strategies, our protocol reveals a path to topological qubit experiments in Kitaev materials at zero applied magnetic field.", "doi": "10.1103/PhysRevLett.129.037201", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2022-07-15", "series_number": "3", "volume": "129", "issue": "3", "pages": "Art. No. 037201" }, { "id": "authors:4z37b-7n608", "collection": "authors", "collection_id": "4z37b-7n608", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220621-285198100", "type": "article", "title": "Evidence for unconventional superconductivity in twisted trilayer graphene", "author": [ { "family_name": "Kim", "given_name": "Hyunjin", "orcid": "0000-0001-9886-0487", "clpid": "Kim-Hyunjin" }, { "family_name": "Choi", "given_name": "Youngjoon", "orcid": "0000-0001-9783-5992", "clpid": "Choi-Youngjoon" }, { "family_name": "Lewandowski", "given_name": "Cyprian", "orcid": "0000-0002-6944-9805", "clpid": "Lewandowski-Cyprian" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Zhang", "given_name": "Yiran", "orcid": "0000-0002-8477-0074", "clpid": "Zhang-Yiran" }, { "family_name": "Polski", "given_name": "Robert", "orcid": "0000-0003-0887-8099", "clpid": "Polski-Robert" }, { "family_name": "Watanabe", "given_name": "Kenji", "orcid": "0000-0003-3701-8119", "clpid": "Watanabe-Kenji" }, { "family_name": "Taniguchi", "given_name": "Takashi", "orcid": "0000-0002-1467-3105", "clpid": "Taniguchi-Takashi" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" } ], "abstract": "Magic-angle twisted trilayer graphene (MATTG) has emerged as a moir\u00e9 material that exhibits strong electronic correlations and unconventional superconductivity. However, local spectroscopic studies of this system are still lacking. Here we perform high-resolution scanning tunnelling microscopy and spectroscopy of MATTG that reveal extensive regions of atomic reconstruction favouring mirror-symmetric stacking. In these regions, we observe symmetry-breaking electronic transitions and doping-dependent band-structure deformations similar to those in magic-angle bilayers, as expected theoretically given the commonality of flat bands. Most notably in a density window spanning two to three holes per moir\u00e9 unit cell, the spectroscopic signatures of superconductivity are manifest as pronounced dips in the tunnelling conductance at the Fermi level accompanied by coherence peaks that become gradually suppressed at elevated temperatures and magnetic fields. The observed evolution of the conductance with doping is consistent with a gate-tunable transition from a gapped superconductor to a nodal superconductor, which is theoretically compatible with a sharp transition from a Bardeen\u2013Cooper\u2013Schrieffer superconductor to a Bose\u2013Einstein-condensation superconductor with a nodal order parameter. Within this doping window, we also detect peak\u2013dip\u2013hump structures that suggest that superconductivity is driven by strong coupling to bosonic modes of MATTG. Our results will enable further understanding of superconductivity and correlated states in graphene-based moir\u00e9 structures beyond twisted bilayers.", "doi": "10.1038/s41586-022-04715-z", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2022-06-16", "series_number": "7914", "volume": "606", "issue": "7914", "pages": "494-500" }, { "id": "authors:qqvh4-vrf77", "collection": "authors", "collection_id": "qqvh4-vrf77", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220524-180301852", "type": "monograph", "title": "Spin-Orbit Enhanced Superconductivity in Bernal Bilayer Graphene", "author": [ { "family_name": "Zhang", "given_name": "Yiran", "orcid": "0000-0002-8477-0074", "clpid": "Zhang-Yiran" }, { "family_name": "Polski", "given_name": "Robert", "orcid": "0000-0003-0887-8099", "clpid": "Polski-Robert-M" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Lantagne-Hurtubise", "given_name": "\u00c9tienne", "orcid": "0000-0003-0417-6452", "clpid": "Lantagne-Hurtubise-\u00c9tienne" }, { "family_name": "Lewandowski", "given_name": "Cyprian", "orcid": "0000-0002-6944-9805", "clpid": "Lewandowski-Cyprian" }, { "family_name": "Zhou", "given_name": "Haoxin", "orcid": "0000-0003-1235-0035", "clpid": "Zhou-Haoxin" }, { "family_name": "Watanabe", "given_name": "Kenji", "orcid": "0000-0003-3701-8119", "clpid": "Watanabe-Kenji" }, { "family_name": "Taniguchi", "given_name": "Takashi", "orcid": "0000-0002-1467-3105", "clpid": "Taniguchi-Takashi" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" } ], "abstract": "In the presence of a large perpendicular electric field, Bernal-stacked bilayer graphene (BLG) features several broken-symmetry metallic phases as well as magnetic-field-induced superconductivity. The superconducting state is quite fragile, however, appearing only in a narrow window of density and with a maximum critical temperature T\ua700 \u2248 30~mK. Here, we show that placing monolayer tungsten diselenide (WSe\u2082) on BLG promotes Cooper pairing to an extraordinary degree: superconductivity appears at zero magnetic field, exhibits an order of magnitude enhancement in T\ua700, and occurs over a density range that is wider by a factor of eight. By mapping quantum oscillations in BLG-WSe\u2082 as a function of electric field and doping, we establish that superconductivity emerges throughout a region whose normal state is polarized, with two out of four spin-valley flavours predominantly populated. In-plane magnetic field measurements further reveal a striking dependence of the critical field on doping, with the Chandrasekhar-Clogston (Pauli) limit roughly obeyed on one end of the superconducting dome yet sharply violated on the other. Moreover, the superconductivity arises only for perpendicular electric fields that push BLG hole wavefunctions towards WSe\u2082 -- suggesting that proximity-induced (Ising) spin-orbit coupling plays a key role in enhancing the pairing. Our results pave the way for engineering robust, highly tunable, and ultra-clean graphene-based superconductors.", "doi": "10.48550/arXiv.2205.05087", "publisher": "arXiv", "publication_date": "2022-05-10" }, { "id": "authors:2jegc-73t42", "collection": "authors", "collection_id": "2jegc-73t42", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220428-212235605", "type": "monograph", "title": "Quantum spin liquids bootstrapped from Ising criticality in Rydberg arrays", "author": [ { "family_name": "Slagle", "given_name": "Kevin", "orcid": "0000-0002-8036-3447", "clpid": "Slagle-Kevin" }, { "family_name": "Liu", "given_name": "Yue", "orcid": "0000-0002-5965-0644", "clpid": "Liu-Yue" }, { "family_name": "Aasen", "given_name": "David", "orcid": "0000-0002-6552-488X", "clpid": "Aasen-David" }, { "family_name": "Pichler", "given_name": "Hannes", "orcid": "0000-0003-2144-536X", "clpid": "Pichler-Hannes" }, { "family_name": "Mong", "given_name": "Roger S. K.", "clpid": "Mong-Roger-S-K" }, { "family_name": "Chen", "given_name": "Xie", "orcid": "0000-0003-2215-2497", "clpid": "Chen-Xie" }, { "family_name": "Endres", "given_name": "Manuel", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Arrays of Rydberg atoms constitute a highly tunable, strongly interacting venue for the pursuit of exotic states of matter. We develop a new strategy for accessing a family of fractionalized phases known as quantum spin liquids in two-dimensional Rydberg arrays. We specifically use effective field theory methods to study arrays assembled from Rydberg chains tuned to an Ising phase transition that famously hosts emergent fermions propagating within each chain. This highly entangled starting point allows us to naturally access spin liquids familiar from Kitaev's honeycomb model, albeit from an entirely different framework. In particular, we argue that finite-range repulsive Rydberg interactions, which frustrate nearby symmetry-breaking orders, can enable coherent propagation of emergent fermions between the chains in which they were born. Delocalization of emergent fermions across the full two-dimensional Rydberg array yields a gapless Z2 spin liquid with a single massless Dirac cone. Here, the Rydberg occupation numbers exhibit universal power-law correlations that provide a straightforward experimental diagnostic of this phase. We further show that explicitly breaking symmetries perturbs the gapless spin liquid into gapped, topologically ordered descendants: Breaking lattice symmetries generates toric-code topological order, whereas introducing chirality generates non-Abelian Ising topological order. In the toric-code phase, we analytically construct microscopic incarnations of non-Abelian defects, which can be created and transported by dynamically controlling the atom positions in the array. Our work suggests that appropriately tuned Rydberg arrays provide a cold-atoms counterpart of solid-state 'Kitaev materials' and, more generally, spotlights a new angle for pursuing experimental platforms for Abelian and non-Abelian fractionalization.", "doi": "10.48550/arXiv.2204.00013", "publisher": "arXiv", "publication_date": "2022-03-31" }, { "id": "authors:j3avd-tf451", "collection": "authors", "collection_id": "j3avd-tf451", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220104-233136449", "type": "article", "title": "Gate-defined wires in twisted bilayer graphene: From electrical detection of intervalley coherence to internally engineered Majorana modes", "author": [ { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Sorensen", "given_name": "Ina M.", "orcid": "0000-0001-6136-9838", "clpid": "Sorensen-Ina-M" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Twisted bilayer graphene (TBG) realizes a highly tunable, strongly interacting system featuring superconductivity and various correlated insulating states. We establish gate-defined wires in TBG with proximity-induced spin-orbit coupling as (i) a tool for revealing the nature of correlated insulators and (ii) a platform for Majorana-based topological qubits. We show that the band structure of a gate-defined wire immersed in an intervalley coherent correlated insulator inherits electrically detectable fingerprints of symmetry breaking native to the latter. Surrounding the wire by a superconducting TBG region on one side and an intervalley coherent correlated insulator on the other further enables the formation of Majorana zero modes\u2014possibly even at zero magnetic field depending on the precise symmetry-breaking order present. Our proposal not only introduces a highly gate-tunable topological qubit medium relying on internally generated proximity effects but can also shed light on the Cooper-pairing mechanism in TBG.", "doi": "10.1103/PhysRevB.105.L081405", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2022-02-15", "series_number": "8", "volume": "105", "issue": "8", "pages": "Art. No. L081405" }, { "id": "authors:3p317-n1h86", "collection": "authors", "collection_id": "3p317-n1h86", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220222-706490000", "type": "article", "title": "Thermal Probes of Phonon-Coupled Kitaev Spin Liquids: From Accurate Extraction of Quantized Edge Transport to Anyon Interferometry", "author": [ { "family_name": "Klocke", "given_name": "Kai", "orcid": "0000-0002-9580-8509", "clpid": "Klocke-Kai" }, { "family_name": "Moore", "given_name": "Joel E.", "clpid": "Moore-Joel-E" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Hal\u00e1sz", "given_name": "G\u00e1bor B.", "clpid": "Hal\u00e1sz-G\u00e1bor-B" } ], "abstract": "Recent theoretical studies inspired by experiments on the Kitaev magnet \u03b1 \u2212 RuCl\u2083 highlight the nontrivial impact of phonons on the thermal Hall conductivity of chiral topological phases. Here, we introduce mixed mesoscopic-macroscopic devices that allow refined thermal-transport probes of non-Abelian spin liquids with Ising topological order. These devices feature a quantum-coherent region with quantized or negligible phonon conductance, flanked by macroscopic lobes that facilitate efficient thermalization between chiral Majorana edge modes and bulk phonons. We show that our devices enable (i) accurate determination of the quantized thermal Hall conductivity, (ii) identification of non-Abelian Ising anyons via the temperature dependence of the thermal conductance, and, most interestingly, (iii) single-anyon detection through heat-based anyon interferometry. Analogous results apply broadly to phonon-coupled chiral topological orders.", "doi": "10.1103/physrevx.12.011034", "issn": "2160-3308", "publisher": "American Physical Society", "publication": "Physical Review X", "publication_date": "2022-01", "series_number": "1", "volume": "12", "issue": "1", "pages": "Art. no. 011034" }, { "id": "authors:n990w-e2f28", "collection": "authors", "collection_id": "n990w-e2f28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220113-234609742", "type": "monograph", "title": "Ascendance of Superconductivity in Magic-Angle Graphene Multilayers", "author": [ { "family_name": "Zhang", "given_name": "Yiran", "orcid": "0000-0002-8477-0074", "clpid": "Zhang-Yiran" }, { "family_name": "Polski", "given_name": "Robert", "orcid": "0000-0003-0887-8099", "clpid": "Polski-Robert-M" }, { "family_name": "Lewandowski", "given_name": "Cyprian", "orcid": "0000-0002-6944-9805", "clpid": "Lewandowski-Cyprian" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Peng", "given_name": "Yang", "orcid": "0000-0002-8868-2928", "clpid": "Peng-Yang" }, { "family_name": "Choi", "given_name": "Youngjoon", "clpid": "Choi-Youngjoon" }, { "family_name": "Kim", "given_name": "Hyunjin", "orcid": "0000-0001-9886-0487", "clpid": "Kim-Hyunjin" }, { "family_name": "Watanabe", "given_name": "Kenji", "orcid": "0000-0003-3701-8119", "clpid": "Watanabe-Kenji" }, { "family_name": "Taniguchi", "given_name": "Takashi", "orcid": "0000-0002-1467-3105", "clpid": "Taniguchi-Takashi" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "von Oppen", "given_name": "Felix", "orcid": "0000-0002-2537-7256", "clpid": "von-Oppen-Felix" }, { "family_name": "Refael", "given_name": "Gil", "clpid": "Refael-G" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" } ], "abstract": "Graphene moire superlattices have emerged as a platform hosting and abundance of correlated insulating, topological, and superconducting phases. While the origins of strong correlations and non-trivial topology are shown to be directly linked to flat moire bands, the nature and mechanism of superconductivity remain enigmatic. In particular, only alternating twisted stacking geometries of bilayer and trilayer graphene are found to exhibit robust superconductivity manifesting as zero resistance and Fraunhofer interference patterns. Here we demonstrate that magic-angle twisted tri-, quadri-, and pentalayers placed on monolayer tungsten diselenide exhibit flavour polarization and superconductivity. We also observe insulating states in the trilayer and quadrilayer arising at finite electric displacement fields, despite the presence of dispersive bands introduced by additional graphene layers. Moreover, the three multilayer geometries allow us to identify universal features in the family of graphene moire structures arising from the intricate relations between superconducting states, symmetry-breaking transitions, and van Hove singularities. Remarkably, as the number of layers increases, superconductivity emerges over a dramatically enhanced filling-factor range. In particular, in twisted pentalayers, superconductivity extends well beyond the filling of four electrons per moire unit cell, demonstrating the non-trivial role of the additional bands. Our results highlight the importance of the interplay between flat and dispersive bands in extending superconducting regions in graphene moire superlattices and open new frontiers for developing graphene-based superconductors.", "doi": "10.48550/arXiv.2112.09270", "publisher": "arXiv", "publication_date": "2021-12-17" }, { "id": "authors:bmxdz-db910", "collection": "authors", "collection_id": "bmxdz-db910", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211207-393208000", "type": "article", "title": "Microscopic characterization of Ising conformal field theory in Rydberg chains", "author": [ { "family_name": "Slagle", "given_name": "Kevin", "orcid": "0000-0002-8036-3447", "clpid": "Slagle-Kevin" }, { "family_name": "Aasen", "given_name": "David", "orcid": "0000-0002-6552-488X", "clpid": "Aasen-David" }, { "family_name": "Pichler", "given_name": "Hannes", "orcid": "0000-0003-2144-536X", "clpid": "Pichler-Hannes" }, { "family_name": "Mong", "given_name": "Roger S. K.", "clpid": "Mong-Roger-S-K" }, { "family_name": "Fendley", "given_name": "Paul", "orcid": "0000-0002-7747-0153", "clpid": "Fendley-Paul" }, { "family_name": "Chen", "given_name": "Xie", "orcid": "0000-0003-2215-2497", "clpid": "Chen-Xie" }, { "family_name": "Endres", "given_name": "Manuel", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Rydberg chains provide an appealing platform for probing conformal field theories (CFTs) that capture universal behavior in a myriad of physical settings. Focusing on a Rydberg chain at the Ising transition separating charge density wave and disordered phases, we establish a detailed link between microscopics and low-energy physics emerging at criticality. We first construct lattice incarnations of primary fields in the underlying Ising CFT including chiral fermions, a nontrivial task given that the Rydberg chain Hamiltonian does not admit an exact fermionization. With this dictionary in hand, we compute correlations of microscopic Rydberg operators, paying special attention to finite, open chains of immediate experimental relevance. We further develop a method to quantify how second-neighbor Rydberg interactions tune the sign and strength of four-fermion couplings in the Ising CFT. Finally, we determine how the Ising fields evolve when four-fermion couplings drive an instability to Ising tricriticality. Our results pave the way to a thorough experimental characterization of Ising criticality in Rydberg arrays, and can inform the design of novel higher-dimensional phases based on coupled critical chains.", "doi": "10.1103/physrevb.104.235109", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2021-12-15", "series_number": "23", "volume": "104", "issue": "23", "pages": "Art. No. 235109" }, { "id": "authors:xvc1e-83a03", "collection": "authors", "collection_id": "xvc1e-83a03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210302-094400352", "type": "article", "title": "Interaction-driven band flattening and correlated phases in twisted bilayer graphene", "author": [ { "family_name": "Choi", "given_name": "Youngjoon", "clpid": "Choi-Youngjoon" }, { "family_name": "Kim", "given_name": "Hyunjin", "orcid": "0000-0001-9886-0487", "clpid": "Kim-Hyunjin" }, { "family_name": "Lewandowski", "given_name": "Cyprian", "orcid": "0000-0002-6944-9805", "clpid": "Lewandowski-Cyprian" }, { "family_name": "Peng", "given_name": "Yang", "orcid": "0000-0002-8868-2928", "clpid": "Peng-Yang" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Polski", "given_name": "Robert", "orcid": "0000-0003-0887-8099", "clpid": "Polski-Robert-M" }, { "family_name": "Zhang", "given_name": "Yiran", "orcid": "0000-0002-8477-0074", "clpid": "Zhang-Yiran" }, { "family_name": "Watanabe", "given_name": "Kenji", "orcid": "0000-0003-3701-8119", "clpid": "Watanabe-Kenji" }, { "family_name": "Taniguchi", "given_name": "Takashi", "orcid": "0000-0002-1467-3105", "clpid": "Taniguchi-Takashi" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" } ], "abstract": "Flat electronic bands, characteristic of 'magic-angle' twisted bilayer graphene, host many correlated phenomena. Nevertheless, many properties of these bands and emerging symmetry-broken phases are still poorly understood. Here we use scanning tunnelling spectroscopy to examine the evolution of the twisted bilayer graphene bands and related gapped phases as the twist angle between the two graphene layers changes. We detect filling-dependent flattening of the bands that is appreciable even when the angle is well above the magic angle value and so the material is nominally in a weakly correlated regime. Upon approaching the magic angle, we further show that the most prominent correlated gaps begin to emerge when band flattening is maximized around certain integer fillings of electrons per moir\u00e9 unit cell. Our observations are consistent with a model that suggests that a significant enhancement of the density of states caused by the band flattening triggers a cascade of symmetry-breaking transitions. Finally, we explore the temperature dependence of the cascade and identify gapped features that develop in a broad range of band fillings where superconductivity is expected. Our results highlight the role of interaction-driven band flattening in defining the electronic properties of twisted bilayer graphene.", "doi": "10.1038/s41567-021-01359-0", "issn": "1745-2473", "publisher": "Nature Publishing Group", "publication": "Nature Physics", "publication_date": "2021-12", "series_number": "12", "volume": "17", "issue": "12", "pages": "1375-1381" }, { "id": "authors:gnrr3-rdt94", "collection": "authors", "collection_id": "gnrr3-rdt94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220113-182244311", "type": "monograph", "title": "Spin chains, defects, and quantum wires for the quantum-double edge", "author": [ { "family_name": "Albert", "given_name": "Victor V.", "orcid": "0000-0002-0335-9508", "clpid": "Albert-Victor-V" }, { "family_name": "Aasen", "given_name": "David", "orcid": "0000-0002-6552-488X", "clpid": "Aasen-David" }, { "family_name": "Xu", "given_name": "Wenqing", "clpid": "Xu-Wenqing-William" }, { "family_name": "Ji", "given_name": "Wenjie", "clpid": "Ji-Wenjie" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Preskill", "given_name": "John", "orcid": "0000-0002-2421-4762", "clpid": "Preskill-J" } ], "abstract": "Non-Abelian defects that bind Majorana or parafermion zero modes are prominent in several topological quantum computation schemes. Underpinning their established understanding is the quantum Ising spin chain, which can be recast as a fermionic model or viewed as a standalone effective theory for the surface-code edge -- both of which harbor non-Abelian defects. We generalize these notions by deriving an effective Ising-like spin chain describing the edge of quantum-double topological order. Relating Majorana and parafermion modes to anyonic strings, we introduce quantum-double generalizations of non-Abelian defects. We develop a way to embed finite-group valued qunits into those valued in continuous groups. Using this embedding, we provide a continuum description of the spin chain and recast its non-interacting part as a quantum wire via addition of a Wess-Zumino-Novikov-Witten term and non-Abelian bosonization.", "doi": "10.48550/arXiv.2111.12096", "publisher": "arXiv", "publication_date": "2021-11-23" }, { "id": "authors:sz595-h0961", "collection": "authors", "collection_id": "sz595-h0961", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220113-182215445", "type": "monograph", "title": "Spectroscopic Signatures of Strong Correlations and Unconventional Superconductivity in Twisted Trilayer Graphene", "author": [ { "family_name": "Kim", "given_name": "Hyunjin", "orcid": "0000-0001-9886-0487", "clpid": "Kim-Hyunjin" }, { "family_name": "Choi", "given_name": "Youngjoon", "clpid": "Choi-Youngjoon" }, { "family_name": "Lewandowski", "given_name": "Cyprian", "orcid": "0000-0002-6944-9805", "clpid": "Lewandowski-Cyprian" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Zhang", "given_name": "Yiran", "orcid": "0000-0002-8477-0074", "clpid": "Zhang-Yiran" }, { "family_name": "Polski", "given_name": "Robert", "orcid": "0000-0003-0887-8099", "clpid": "Polski-Robert-M" }, { "family_name": "Watanabe", "given_name": "Kenji", "orcid": "0000-0003-3701-8119", "clpid": "Watanabe-Kenji" }, { "family_name": "Taniguchi", "given_name": "Takashi", "orcid": "0000-0002-1467-3105", "clpid": "Taniguchi-Takashi" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" } ], "abstract": "Magic-angle twisted trilayer graphene (MATTG) has emerged as a novel moir\u00e9 material that exhibits both strong electronic correlations and unconventional superconductivity. However, spectroscopic studies of its electronic properties are lacking, and the nature of superconductivity and the corresponding order parameter in this system remain elusive. Here we perform high-resolution scanning tunneling microscopy and spectroscopy of MATTG and reveal extensive regions of atomic reconstruction that favor mirror-symmetric stacking. In these regions, we observe a cascade of symmetry-breaking electronic transitions and doping-dependent band structure deformations similar to those realized in magic-angle bilayers, as expected theoretically given the commonality of flat bands. More strikingly, in a density window spanning two to three holes per moire unit cell, spectroscopic signatures of superconductivity are manifest as pronounced dips in the tunneling conductance at the Fermi level accompanied by coherence peaks that become gradually suppressed at elevated temperatures and magnetic fields. The observed evolution of the conductance with doping is consistent with a gate-tunable transition from a gapped to a nodal superconductor, which we show theoretically is compatible with a sharp transition from a Bardeen-Cooper-Schrieffer (BCS) to a Bose-Einstein condensation (BEC) superconductor with a nodal order parameter. Within this doping window, we also detect peak-dip-hump structures suggesting that superconductivity is driven by strong coupling to bosonic modes of MATTG. Our results pave the way for further understanding of superconductivity and correlated states in graphene-based moir\u00e9 structures beyond twisted bilayers, where unconventional superconductivity and nodal pairing were reported.", "doi": "10.48550/arXiv.2109.12127", "publisher": "arXiv", "publication_date": "2021-09-24" }, { "id": "authors:trrzm-8xw29", "collection": "authors", "collection_id": "trrzm-8xw29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220104-233139832", "type": "monograph", "title": "Thermal anyon interferometry in phonon-coupled Kitaev spin liquids", "author": [ { "family_name": "Klocke", "given_name": "Kai", "orcid": "0000-0002-9580-8509", "clpid": "Klocke-Kai" }, { "family_name": "Moore", "given_name": "Joel E.", "clpid": "Moore-Joel-E" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Hal\u00e1sz", "given_name": "G\u00e1bor B.", "clpid": "Hal\u00e1sz-G\u00e1bor-B" } ], "abstract": "Recent theoretical studies inspired by experiments on the Kitaev magnet \u03b1-RuCl\u2083 highlight the nontrivial impact of phonons on the thermal Hall conductivity of chiral topological phases. Here we introduce mixed mesoscopic-macroscopic devices that allow refined thermal-transport probes of non-Abelian spin liquids with Ising topological order. These devices feature a quantum-coherent mesoscopic region with negligible phonon conductance, flanked by macroscopic lobes that facilitate efficient thermalization between chiral Majorana edge modes and bulk phonons. We show that our devices enable (i) accurate determination of the quantized thermal Hall conductivity, (ii) identification of non-Abelian Ising anyons via the temperature dependence of the thermal conductance, and most interestingly (iii) single-anyon detection through heat-based anyon interferometry. Analogous results apply broadly to phonon-coupled chiral topological orders.", "doi": "10.48550/arXiv.2105.05869", "publisher": "arXiv", "publication_date": "2021-05-12" }, { "id": "authors:n35hk-1cx37", "collection": "authors", "collection_id": "n35hk-1cx37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201111-081453060", "type": "article", "title": "Time-Domain Anyon Interferometry in Kitaev Honeycomb Spin Liquids and Beyond", "author": [ { "family_name": "Klocke", "given_name": "Kai", "orcid": "0000-0002-9580-8509", "clpid": "Klocke-Kai" }, { "family_name": "Aasen", "given_name": "David", "orcid": "0000-0002-6552-488X", "clpid": "Aasen-David" }, { "family_name": "Mong", "given_name": "Roger S. K.", "clpid": "Mong-Roger-S-K" }, { "family_name": "Demler", "given_name": "Eugene A.", "orcid": "0000-0002-2499-632X", "clpid": "Demler-Eugene-A" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Motivated by recent experiments on the Kitaev honeycomb magnet \u03b1-RuCl\u2083, we introduce time-domain probes of the edge and quasiparticle content of non-Abelian spin liquids. Our scheme exploits ancillary quantum spins that communicate via time-dependent tunneling of energy into and out of the spin liquid's chiral Majorana edge state. We show that the ancillary-spin dynamics reveals the edge-state velocity and, in suitable geometries, detects individual non-Abelian anyons and emergent fermions via a time-domain counterpart of quantum-Hall anyon interferometry. We anticipate applications to a wide variety of topological phases in solid-state and cold-atoms settings.", "doi": "10.1103/PhysRevLett.126.177204", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2021-04-30", "series_number": "17", "volume": "126", "issue": "17", "pages": "Art. No. 177204" }, { "id": "authors:gxma1-b2m80", "collection": "authors", "collection_id": "gxma1-b2m80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210421-103423569", "type": "article", "title": "Topological superconductivity in nanowires proximate to a diffusive superconductor\u2013magnetic-insulator bilayer", "author": [ { "family_name": "Khindanov", "given_name": "Aleksei", "orcid": "0000-0003-4101-0259", "clpid": "Khindanov-Aleksei" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Lee", "given_name": "Patrick", "clpid": "Lee-Patrick-A" }, { "family_name": "Cole", "given_name": "William S.", "clpid": "Cole-William-S" }, { "family_name": "Antipov", "given_name": "Andrey E.", "orcid": "0000-0002-4987-7183", "clpid": "Antipov-Andrey-E" } ], "abstract": "We study semiconductor nanowires coupled to a bilayer of a disordered superconductor and a magnetic insulator, motivated by recent experiments reporting possible Majorana-zero-mode signatures in related architectures. Specifically, we pursue a quasiclassical Usadel equation approach that treats superconductivity in the bilayer self-consistently in the presence of spin-orbit scattering, magnetic-impurity scattering, and Zeeman splitting induced by both the magnetic insulator and a supplemental applied field. Within this framework we explore prospects for engineering topological superconductivity in a nanowire proximate to the bilayer. We find that a magnetic-insulator-induced Zeeman splitting, mediated through the superconductor alone, cannot induce a topological phase since the destruction of superconductivity (i.e., Clogston limit) preempts the required regime in which the nanowire's Zeeman energy exceeds the induced pairing strength. However, this Zeeman splitting does reduce the critical applied field needed to access the topological phase transition, with fields antiparallel to the magnetization of the magnetic insulator having an optimal effect. Finally, we show that magnetic-impurity scattering degrades the topological phase, and spin-orbit scattering, if present in the superconductor, pushes the Clogston limit to higher fields yet simultaneously increases the critical applied field strength.", "doi": "10.1103/physrevb.103.134506", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2021-04-01", "series_number": "13", "volume": "103", "issue": "13", "pages": "Art. No. 134506" }, { "id": "authors:py9t4-2y660", "collection": "authors", "collection_id": "py9t4-2y660", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191216-103049254", "type": "article", "title": "Recovery of massless Dirac fermions at charge neutrality in strongly interacting twisted bilayer graphene with disorder", "author": [ { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Stacking two graphene layers twisted by the magic angle \u03b8\u22481.1\u2218 generates flat energy bands, which in turn catalyzes various strongly correlated phenomena depending on filling and sample details. At charge neutrality, transport measurements reveal superficially mundane semimetallicity (as expected when correlations are weak) in some samples yet robust insulation in others. We propose that the interplay between interactions and disorder admits either behavior, even when the system is strongly correlated and locally gapped. Specifically, we argue that strong interactions supplemented by weak, smooth disorder stabilize a network of gapped quantum valley Hall domains with spatially varying Chern numbers determined by the disorder landscape\u2014even when an entirely different order is favored in the clean limit. Within this scenario, sufficiently small samples that realize a single domain display insulating transport characteristics. Conversely, multidomain samples exhibit re-emergent massless Dirac fermions formed by gapless domain-wall modes, yielding semimetallic behavior except on the ultralong scales at which localization becomes visible. We discuss experimental tests of this proposal via local probes and transport. Our results highlight the crucial role that randomness can play in ground-state selection of twisted heterostructures, an observation that we expect to have further ramifications at other fillings.", "doi": "10.1103/PhysRevB.103.125138", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2021-03-15", "series_number": "12", "volume": "103", "issue": "12", "pages": "Art. No. 125138" }, { "id": "authors:zb5x8-zyx34", "collection": "authors", "collection_id": "zb5x8-zyx34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200922-103631989", "type": "article", "title": "Correlation-driven topological phases in magic-angle twisted bilayer graphene", "author": [ { "family_name": "Choi", "given_name": "Youngjoon", "clpid": "Choi-Youngjoon" }, { "family_name": "Kim", "given_name": "Hyunjin", "orcid": "0000-0001-9886-0487", "clpid": "Kim-Hyunjin" }, { "family_name": "Peng", "given_name": "Yang", "orcid": "0000-0002-8868-2928", "clpid": "Peng-Yang" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Lewandowski", "given_name": "Cyprian", "clpid": "Lewandowski-Cyprian" }, { "family_name": "Polski", "given_name": "Robert", "orcid": "0000-0003-0887-8099", "clpid": "Polski-Robert-M" }, { "family_name": "Zhang", "given_name": "Yiran", "orcid": "0000-0002-8477-0074", "clpid": "Zhang-Yiran" }, { "family_name": "Arora", "given_name": "Harpreet Singh", "orcid": "0000-0002-7674-735X", "clpid": "Arora-Harpreet-Singh" }, { "family_name": "Watanabe", "given_name": "Kenji", "orcid": "0000-0003-3701-8119", "clpid": "Watanabe-Kenji" }, { "family_name": "Taniguchi", "given_name": "Takashi", "clpid": "Taniguchi-Takashi" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" } ], "abstract": "Magic-angle twisted bilayer graphene (MATBG) exhibits a range of correlated phenomena that originate from strong electron\u2013electron interactions. These interactions make the Fermi surface highly susceptible to reconstruction when \u00b11, \u00b12 and \u00b13 electrons occupy each moir\u00e9 unit cell, and lead to the formation of various correlated phases. Although some phases have been shown to have a non-zero Chern number, the local microscopic properties and topological character of many other phases have not yet been determined. Here we introduce a set of techniques that use scanning tunnelling microscopy to map the topological phases that emerge in MATBG in a finite magnetic field. By following the evolution of the local density of states at the Fermi level with electrostatic doping and magnetic field, we create a local Landau fan diagram that enables us to assign Chern numbers directly to all observed phases. We uncover the existence of six topological phases that arise from integer fillings in finite fields and that originate from a cascade of symmetry-breaking transitions driven by correlations. These topological phases can form only for a small range of twist angles around the magic angle, which further differentiates them from the Landau levels observed near charge neutrality. Moreover, we observe that even the charge-neutrality Landau spectrum taken at low fields is considerably modified by interactions, exhibits prominent electron\u2013hole asymmetry, and features an unexpectedly large splitting between zero Landau levels (about 3 to 5 millielectronvolts). Our results show how strong electronic interactions affect the MATBG band structure and lead to correlation-enabled topological phases.", "doi": "10.1038/s41586-020-03159-7", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2021-01-28", "series_number": "7843", "volume": "589", "issue": "7843", "pages": "536-541" }, { "id": "authors:j1b54-dtv79", "collection": "authors", "collection_id": "j1b54-dtv79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201112-103611049", "type": "article", "title": "Fragility of the Fractional Josephson Effect in Time-Reversal-Invariant Topological Superconductors", "author": [ { "family_name": "Knapp", "given_name": "Christina", "orcid": "0000-0002-5982-8107", "clpid": "Knapp-Christina" }, { "family_name": "Chew", "given_name": "Aaron", "orcid": "0000-0003-0448-6215", "clpid": "Chew-Aaron" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Time-reversal-invariant topological superconductor (TRITOPS) wires host Majorana Kramers pairs that have been predicted to mediate a fractional Josephson effect with 4\u03c0 periodicity in the superconducting phase difference. We explore the TRITOPS fractional Josephson effect in the presence of time-dependent \"local mixing\" perturbations that instantaneously preserve time-reversal symmetry. Specifically, we show that just as such couplings render braiding of Majorana Kramers pairs nonuniversal, the Josephson current becomes either aperiodic or 2\u03c0 periodic (depending on conditions that we quantify) unless the phase difference is swept sufficiently quickly. We further analyze topological superconductors with \nT\u00b2 = +1 time-reversal symmetry and reveal a rich interplay between interactions and local mixing that can be experimentally probed in nanowire arrays.", "doi": "10.1103/physrevlett.125.207002", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2020-11-13", "series_number": "20", "volume": "125", "issue": "20", "pages": "Art. No. 207002" }, { "id": "authors:7yxgs-9qf25", "collection": "authors", "collection_id": "7yxgs-9qf25", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200225-102617489", "type": "article", "title": "Superconductivity in metallic twisted bilayer graphene stabilized by WSe\u2082", "author": [ { "family_name": "Arora", "given_name": "Harpreet Singh", "orcid": "0000-0002-7674-735X", "clpid": "Arora-H-S" }, { "family_name": "Polski", "given_name": "Robert", "orcid": "0000-0003-0887-8099", "clpid": "Polski-R-M" }, { "family_name": "Zhang", "given_name": "Yiran", "orcid": "0000-0002-8477-0074", "clpid": "Zhang-Yiran" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Choi", "given_name": "Youngjoon", "clpid": "Choi-Youngjoon" }, { "family_name": "Kim", "given_name": "Hyunjin", "orcid": "0000-0001-9886-0487", "clpid": "Kim-Hyunjin" }, { "family_name": "Lin", "given_name": "Zhong", "clpid": "Lin-Zhong" }, { "family_name": "Wilson", "given_name": "Ilham Zaky", "clpid": "Wilson-I-Z" }, { "family_name": "Xu", "given_name": "Xiaodong", "clpid": "Xu-Xiaodong" }, { "family_name": "Chu", "given_name": "Jiun-Haw", "clpid": "Chu-Jiun-Haw" }, { "family_name": "Watanabe", "given_name": "Kenji", "orcid": "0000-0003-3701-8119", "clpid": "Watanabe-Kenji" }, { "family_name": "Taniguchi", "given_name": "Takashi", "clpid": "Taniguchi-Takashi" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" } ], "abstract": "Magic-angle twisted bilayer graphene (TBG), with rotational misalignment close to 1.1 degrees, features isolated flat electronic bands that host a rich phase diagram of correlated insulating, superconducting, ferromagnetic and topological phases. Correlated insulators and superconductivity have been previously observed only for angles within 0.1 degree of the magic angle and occur in adjacent or overlapping electron-density ranges; nevertheless, the origins of these states and the relation between them remain unclear, owing to their sensitivity to microscopic details. Beyond twist angle and strain, the dependence of the TBG phase diagram on the alignment and thickness of the insulating hexagonal boron nitride (hBN) used to encapsulate the graphene sheets indicates the importance of the microscopic dielectric environment. Here we show that adding an insulating tungsten diselenide (WSe\u2082) monolayer between the hBN and the TBG stabilizes superconductivity at twist angles much smaller than the magic angle. For the smallest twist angle of 0.79 degrees, superconductivity is still observed despite the TBG exhibiting metallic behaviour across the whole range of electron densities. Finite-magnetic-field measurements further reveal weak antilocalization signatures as well as breaking of fourfold spin\u2013valley symmetry, consistent with spin\u2013orbit coupling induced in the TBG via its proximity to WSe\u2082. Our results constrain theoretical explanations for the emergence of superconductivity in TBG and open up avenues towards engineering quantum phases in moir\u00e9 systems.", "doi": "10.1038/s41586-020-2473-8", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2020-07-16", "series_number": "7816", "volume": "583", "issue": "7816", "pages": "379-384" }, { "id": "authors:sk5dj-qjx89", "collection": "authors", "collection_id": "sk5dj-qjx89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200225-103848261", "type": "article", "title": "Electrical Probes of the Non-Abelian Spin Liquid in Kitaev Materials", "author": [ { "family_name": "Aasen", "given_name": "David", "orcid": "0000-0002-6552-488X", "clpid": "Aasen-D" }, { "family_name": "Mong", "given_name": "Roger S. K.", "clpid": "Mong-Roger-S-K" }, { "family_name": "Hunt", "given_name": "Benjamin M.", "orcid": "0000-0002-5008-8042", "clpid": "Hunt-B-M" }, { "family_name": "Mandrus", "given_name": "David", "orcid": "0000-0003-3616-7104", "clpid": "Mandrus-D" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Recent thermal-conductivity measurements evidence a magnetic-field-induced non-Abelian spin-liquid phase in the Kitaev material \u03b1\u2212RuCl\u2083. Although the platform is a good Mott insulator, we propose experiments that electrically probe the spin liquid's hallmark chiral Majorana edge state and bulk anyons, including their exotic exchange statistics. We specifically introduce circuits that exploit interfaces between electrically active systems and Kitaev materials to \"perfectly\" convert electrons from the former into emergent fermions in the latter\u2014thereby enabling variations of transport probes invented for topological superconductors and fractional quantum-Hall states. Along the way, we resolve puzzles in the literature concerning interacting Majorana fermions, and also develop an anyon-interferometry framework that incorporates nontrivial energy-partitioning effects. Our results illuminate a partial pathway toward topological quantum computation with Kitaev materials.", "doi": "10.1103/PhysRevX.10.031014", "issn": "2160-3308", "publisher": "American Physical Society", "publication": "Physical Review X", "publication_date": "2020-07", "series_number": "3", "volume": "10", "issue": "3", "pages": "Art. No. 031014" }, { "id": "authors:wec65-tmt62", "collection": "authors", "collection_id": "wec65-tmt62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200727-084626398", "type": "monograph", "title": "Survival of the fractional Josephson effect in time-reversal-invariant topological superconductors", "author": [ { "family_name": "Knapp", "given_name": "Christina", "orcid": "0000-0002-5982-8107", "clpid": "Knapp-Christina" }, { "family_name": "Chew", "given_name": "Aaron", "orcid": "0000-0003-0448-6215", "clpid": "Chew-Aaron" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Time-reversal-invariant topological superconductor (TRITOPS) wires host Majorana Kramers pairs that have been predicted to mediate a fractional Josephson effect with 4\u03c0 periodicity in the superconducting phase difference. We explore the TRITOPS fractional Josephson effect in the presence of time-dependent `local mixing' perturbations that instantaneously preserve time-reversal symmetry. Specifically, we show that just as such couplings render braiding of Majorana Kramers pairs non-universal, the Josephson current becomes either aperiodic or 2\u03c0-periodic (depending on conditions that we quantify) unless the phase difference is swept sufficiently quickly. We further analyze topological superconductors with T\u00b2 = +1 time-reversal symmetry and reveal a rich interplay between interactions and local mixing that can be experimentally probed in nanowire arrays.", "doi": "10.48550/arXiv.2006.10772", "publisher": "arXiv", "publication_date": "2020-06-18" }, { "id": "authors:ea74h-5mr81", "collection": "authors", "collection_id": "ea74h-5mr81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191014-105123769", "type": "article", "title": "Time-crystalline Topological Superconductors", "author": [ { "family_name": "Chew", "given_name": "Aaron", "orcid": "0000-0003-0448-6215", "clpid": "Chew-Aaron" }, { "family_name": "Mross", "given_name": "David F.", "orcid": "0000-0002-6585-1469", "clpid": "Mross-D-F" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Time crystals form when arbitrary physical states of a periodically driven system spontaneously break discrete time-translation symmetry. We introduce one-dimensional time-crystalline topological superconductors, for which time-translation symmetry breaking and topological physics intertwine\u2014yielding anomalous Floquet Majorana modes that are not possible in free-fermion systems. Such a phase exhibits a bulk magnetization that returns to its original form after two drive periods, together with Majorana end modes that recover their initial form only after four drive periods. We propose experimental implementations and detection schemes for this new state.", "doi": "10.1103/PhysRevLett.124.096802", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2020-03-06", "series_number": "9", "volume": "124", "issue": "9", "pages": "Art. No. 096802" }, { "id": "authors:rej3e-3ed94", "collection": "authors", "collection_id": "rej3e-3ed94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200203-105634945", "type": "article", "title": "Dephasing and leakage dynamics of noisy Majorana-based qubits: Topological versus Andreev", "author": [ { "family_name": "Mishmash", "given_name": "Ryan V.", "clpid": "Mishmash-R-V" }, { "family_name": "Bauer", "given_name": "Bela", "orcid": "0000-0001-9796-2115", "clpid": "Bauer-B" }, { "family_name": "von Oppen", "given_name": "Felix", "clpid": "von-Oppen-F" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Topological quantum computation encodes quantum information nonlocally by nucleating non-Abelian anyons separated by distances \nL, typically spanning the qubit device size. This nonlocality renders topological qubits exponentially immune to dephasing from all sources of classical noise with operator support local on the scale of \nL. We perform detailed analytical and numerical analyses of a time-domain Ramsey-type protocol for noisy Majorana-based qubits that is designed to validate this coveted topological protection in near-term devices such as the so-called \"tetron\" design. By assessing dependence of dephasing times on tunable parameters, e.g., magnetic field, our proposed protocol can clearly distinguish a bona fide Majorana qubit from one constructed from semilocal Andreev bound states, which can otherwise closely mimic the true topological scenario in local probes. In addition, we analyze leakage of the qubit out of its low-energy manifold due to classical-noise-induced generation of quasiparticle excitations; leakage limits the qubit lifetime when the bulk gap collapses, and hence our protocol further reveals the onset of a topological phase transition. This experiment requires measurement of two nearby Majorana modes for both initialization and readout\u2014achievable, for example, by tunnel coupling to a nearby quantum dot\u2014but no further Majorana manipulations, and thus constitutes an enticing prebraiding experiment. Along the way, we address conceptual subtleties encountered when discussing dephasing and leakage in the context of Majorana qubits.", "doi": "10.1103/physrevb.101.075404", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2020-02-15", "series_number": "7", "volume": "101", "issue": "7", "pages": "Art. No. 075404" }, { "id": "authors:a69vz-3xp68", "collection": "authors", "collection_id": "a69vz-3xp68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190426-084652512", "type": "article", "title": "Electronic correlations in twisted bilayer graphene near the magic angle", "author": [ { "family_name": "Choi", "given_name": "Youngjoon", "clpid": "Choi-Youngjoon" }, { "family_name": "Kemmer", "given_name": "Jeannette", "clpid": "Kemmer-Jeanette" }, { "family_name": "Peng", "given_name": "Yang", "orcid": "0000-0002-8868-2928", "clpid": "Peng-Yang" }, { "family_name": "Thomson", "given_name": "Alex", "orcid": "0000-0002-9938-5048", "clpid": "Thomson-Alex" }, { "family_name": "Arora", "given_name": "Harpreet", "orcid": "0000-0002-7674-735X", "clpid": "Arora-H-S" }, { "family_name": "Polski", "given_name": "Robert", "orcid": "0000-0003-0887-8099", "clpid": "Polski-R-M" }, { "family_name": "Zhang", "given_name": "Yiran", "orcid": "0000-0002-8477-0074", "clpid": "Zhang-Yiran" }, { "family_name": "Ren", "given_name": "Hechen", "clpid": "Ren-Hechen" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Refael", "given_name": "Gil", "clpid": "Refael-G" }, { "family_name": "von Oppen", "given_name": "Felix", "clpid": "von-Oppen-F" }, { "family_name": "Watanabe", "given_name": "Kenji", "orcid": "0000-0003-3701-8119", "clpid": "Watanabe-Kenji" }, { "family_name": "Taniguchi", "given_name": "Takashi", "clpid": "Taniguchi-Takashi" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" } ], "abstract": "Twisted bilayer graphene with a twist angle of around 1.1\u00b0 features a pair of isolated flat electronic bands and forms a platform for investigating strongly correlated electrons. Here, we use scanning tunnelling microscopy to probe the local properties of highly tunable twisted bilayer graphene devices and show that the flat bands deform when aligned with the Fermi level. When the bands are half-filled, we observe the development of gaps originating from correlated insulating states. Near charge neutrality, we find a previously unidentified correlated regime featuring an enhanced splitting of the flat bands. We describe this within a microscopic model that predicts a strong tendency towards nematic ordering. Our results provide insights into symmetry-breaking correlation effects and highlight the importance of electronic interactions for all filling fractions in twisted bilayer graphene.", "doi": "10.1038/s41567-019-0606-5", "issn": "1745-2473", "publisher": "Nature Publishing Group", "publication": "Nature Physics", "publication_date": "2019-11", "series_number": "11", "volume": "15", "issue": "11", "pages": "1174-1180" }, { "id": "authors:pjt7y-cac80", "collection": "authors", "collection_id": "pjt7y-cac80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191004-085117901", "type": "article", "title": "Commuting-projector Hamiltonians for two-dimensional topological insulators: Edge physics and many-body invariants", "author": [ { "family_name": "Son", "given_name": "Jun Ho", "clpid": "Son-Jun-Ho" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Inspired by a recently constructed commuting-projector Hamiltonian for a two-dimensional (2D) time-reversal-invariant topological superconductor [Z. Wang et al., Phys. Rev. B 98, 094502 (2018)], we introduce a commuting-projector model that describes an interacting yet exactly solvable 2D topological insulator. We explicitly show that both the gapped and gapless boundaries of our model are consistent with those of band-theoretic, weakly interacting topological insulators. Interestingly, on certain lattices our time-reversal-symmetric models also enjoy CP symmetry, leading to intuitive interpretations of the bulk invariant for a CP-symmetric topological insulator upon putting the system on a Klein bottle. We also briefly discuss how these many-body invariants may be able to characterize models with only time-reversal symmetry.", "doi": "10.1103/physrevb.100.155107", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2019-10-15", "series_number": "15", "volume": "100", "issue": "15", "pages": "Art. No. 155107" }, { "id": "authors:e1jc2-2hg09", "collection": "authors", "collection_id": "e1jc2-2hg09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190426-083534979", "type": "article", "title": "Quantum anomalous parity Hall effect in magnetically disordered topological insulator films", "author": [ { "family_name": "Haim", "given_name": "Arbel", "clpid": "Haim-Arbel" }, { "family_name": "Ilan", "given_name": "Roni", "clpid": "Ilan-Roni" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "In magnetically doped thin-film topological insulators, aligning the magnetic moments generates a quantum anomalous Hall phase supporting a single chiral edge state. We show that as the system demagnetizes, disorder from randomly oriented magnetic moments can produce a \"quantum anomalous parity Hall\" phase with helical edge modes protected by a unitary reflection symmetry. We further show that introducing superconductivity, combined with selective breaking of reflection symmetry by a gate, allows for creation and manipulation of Majorana zero modes via purely electrical means and at zero applied magnetic field.", "doi": "10.1103/PhysRevLett.123.046801", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2019-07-26", "series_number": "4", "volume": "123", "issue": "4", "pages": "Art. No. 046801" }, { "id": "authors:n37c4-2h811", "collection": "authors", "collection_id": "n37c4-2h811", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171004-145628173", "type": "article", "title": "Robust helical edge transport in quantum spin Hall quantum wells", "author": [ { "family_name": "Skolasinski", "given_name": "Rafal", "clpid": "Skolasinski-R" }, { "family_name": "Pikulin", "given_name": "Dmitry I.", "clpid": "Pikulin-D-I" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Wimmer", "given_name": "Michael", "clpid": "Wimmer-M" } ], "abstract": "We show that edge-state transport in semiconductor-based quantum spin Hall systems is unexpectedly robust to magnetic fields. The origin for this robustness lies in an intrinsic suppression of the edge-state g-factor and the fact that the edge-state Dirac point is typically hidden in the valence band. A detailed k\u22c5p band-structure analysis reveals that both InAs/GaSb and HgTe/CdTe quantum wells exhibit such buried Dirac points for a wide range of well thicknesses. By simulating transport in a disordered system described within an effective model, we demonstrate that edge-state transport remains nearly quantized up to large magnetic fields, consistent with recent experiments.", "doi": "10.1103/PhysRevB.98.201404", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2018-11-15", "series_number": "20", "volume": "98", "issue": "20", "pages": "Art. No. 201404" }, { "id": "authors:cvb7q-gjv34", "collection": "authors", "collection_id": "cvb7q-gjv34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180906-130214378", "type": "article", "title": "Noise-Induced Backscattering in a Quantum Spin Hall Edge", "author": [ { "family_name": "V\u00e4yrynen", "given_name": "Jukka I.", "clpid": "V\u00e4yrynen-J-I" }, { "family_name": "Pikulin", "given_name": "Dmitry I.", "clpid": "Pikulin-D-I" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Time-reversal symmetry suppresses electron backscattering in a quantum-spin-Hall edge, yielding quantized conductance at zero temperature. Understanding the dominant corrections in finite-temperature experiments remains an unsettled issue. We study a novel mechanism for conductance suppression: backscattering caused by incoherent electromagnetic noise. Specifically, we show that an electric potential fluctuating randomly in time can backscatter electrons inelastically without constraints faced by electron-electron interactions. We quantify noise-induced corrections to the dc conductance in various regimes and propose an experiment to test this scenario.", "doi": "10.1103/PhysRevLett.121.106601", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2018-09-07", "series_number": "10", "volume": "121", "issue": "10", "pages": "Art. No. 106601" }, { "id": "authors:yr4bq-06f32", "collection": "authors", "collection_id": "yr4bq-06f32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180810-093237801", "type": "article", "title": "Numerical exploration of trial wave functions for the particle-hole-symmetric Pfaffian", "author": [ { "family_name": "Mishmash", "given_name": "Ryan V.", "clpid": "Mishmash-R-V" }, { "family_name": "Mross", "given_name": "David F.", "orcid": "0000-0002-6585-1469", "clpid": "Mross-D-F" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Motrunich", "given_name": "Olexei I.", "orcid": "0000-0001-8031-0022", "clpid": "Motrunich-Olexei" } ], "abstract": "We numerically assess model wave functions for the recently proposed particle-hole-symmetric Pfaffian (\"PH-Pfaffian\") topological order, a phase consistent with the recently reported thermal Hall conductance [M. Banerjee et al., Nature 559, 205 (2018)] at the ever enigmatic \u03bd = 5/2 quantum Hall plateau. We find that the most natural Moore-Read-inspired trial state for the PH-Pfaffian, when projected into the lowest Landau level, exhibits a remarkable numerical similarity on accessible system sizes with the corresponding (compressible) composite Fermi liquid. Consequently, this PH-Pfaffian trial state performs reasonably well energetically in the half-filled lowest Landau level, but is likely not a good starting point for understanding the \u03bd = 5/2 ground state. Our results suggest that the PH-Pfaffian model wave function either encodes anomalously weak p-wave pairing of composite fermions or fails to represent a gapped, incompressible phase altogether.", "doi": "10.1103/PhysRevB.98.081107", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2018-08-15", "series_number": "8", "volume": "98", "issue": "8", "pages": "Art. No. 081107" }, { "id": "authors:qhhnk-rga96", "collection": "authors", "collection_id": "qhhnk-rga96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180827-094621499", "type": "article", "title": "Fermionized parafermions and symmetry-enriched Majorana modes", "author": [ { "family_name": "Chew", "given_name": "Aaron", "orcid": "0000-0003-0448-6215", "clpid": "Chew-Aaron" }, { "family_name": "Mross", "given_name": "David F.", "orcid": "0000-0002-6585-1469", "clpid": "Mross-D-F" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Parafermion zero modes are generalizations of Majorana modes that underlie comparatively rich non-Abelian-anyon properties. We introduce exact mappings that connect parafermion chains, which can emerge in two-dimensional fractionalized media, to strictly one-dimensional fermionic systems. In particular, we show that parafermion zero modes in the former setting translate into symmetry-enriched Majorana modes that intertwine with a bulk order parameter\u2014yielding braiding and fusion properties that are impossible in standard Majorana platforms. Fusion characteristics of symmetry-enriched Majorana modes are directly inherited from the associated parafermion setup and can be probed via two kinds of anomalous pumping cycles that we construct. Most notably, our mappings relate \u2124_4 parafermions to conventional electrons with time-reversal symmetry. In this case, one of our pumping protocols entails fairly minimal experimental requirements: Cycling a weakly correlated wire between a trivial phase and time-reversal-invariant topological superconducting state produces an edge magnetization with quadrupled periodicity. Our work highlights new avenues for exploring beyond-Majorana physics in experimentally relevant one-dimensional electronic platforms, including proximitized ferromagnetic chains.", "doi": "10.1103/physrevb.98.085143", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2018-08-15", "series_number": "8", "volume": "98", "issue": "8", "pages": "Art. No. 085143" }, { "id": "authors:jnxz7-vm170", "collection": "authors", "collection_id": "jnxz7-vm170", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190521-132353909", "type": "article", "title": "Dynamics of Majorana-based qubits operated with an array of tunable gates", "author": [ { "family_name": "Bauer", "given_name": "Bela", "orcid": "0000-0001-9796-2115", "clpid": "Bauer-B" }, { "family_name": "Karzig", "given_name": "Torsten", "orcid": "0000-0003-0834-0547", "clpid": "Karzig-T" }, { "family_name": "Mishmash", "given_name": "Ryan V.", "clpid": "Mishmash-R-V" }, { "family_name": "Antipov", "given_name": "Andrey E.", "orcid": "0000-0002-4987-7183", "clpid": "Antipov-A-E" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "We study the dynamics of Majorana zero modes that are shuttled via local tuning of the electrochemical potential in a superconducting wire. By performing time-dependent simulations of microscopic lattice models, we show that diabatic corrections associated with the moving Majorana modes are quantitatively captured by a simple Landau-Zener description. We further simulate a Rabi-oscillation protocol in a specific qubit design with four Majorana zero modes in a single wire and quantify constraints on the timescales for performing qubit operations in this setup. Our simulations utilize a Majorana representation of the system, which greatly simplifies simulations of superconductors at the mean-field level.", "doi": "10.21468/SciPostPhys.5.1.004", "issn": "2542-4653", "publisher": "SciPost", "publication": "SciPost Physics", "publication_date": "2018-07-19", "series_number": "1", "volume": "5", "issue": "1", "pages": "Art. No. 004" }, { "id": "authors:cjbwz-w9k20", "collection": "authors", "collection_id": "cjbwz-w9k20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180709-130559395", "type": "article", "title": "A Hot Topic in the Quantum Hall Effect", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Heat transport studies of fractional quantum Hall systems provide evidence for a new phase of matter with potential applications in fault-tolerant quantum computation.", "doi": "10.1103/Physics.11.70", "issn": "1943-2879", "publisher": "American Physical Society", "publication": "Physics", "publication_date": "2018-07-09", "volume": "11", "pages": "Art. No. 70" }, { "id": "authors:8rf02-5ww34", "collection": "authors", "collection_id": "8rf02-5ww34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180626-130432855", "type": "article", "title": "Commuting-projector Hamiltonians for chiral topological phases built from parafermions", "author": [ { "family_name": "Son", "given_name": "Jun Ho", "clpid": "Son-Jun-Ho" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "We introduce a family of commuting-projector Hamiltonians whose degrees of freedom involve \u2124_3 parafermion zero modes residing in a parent fractional-quantum-Hall fluid. These commuting-projector models inherit nontrivial Hall conductance from the parent quantum-Hall states in which they are defined, and thus can describe chiral topological phases. The two simplest models in this family emerge from dressing Ising-paramagnet and toric-code spin models with parafermions; we study their edge properties, anyonic excitations, and ground-state degeneracy. We show that the first model realizes a symmetry-enriched topological phase (SET) for which \u2124_2 spin-flip symmetry from the Ising paramagnet permutes the anyons. Interestingly, the interface between this SET and the parent quantum-Hall phase realizes symmetry-enforced \u2124_3 parafermion criticality with no fine-tuning required. The second model exhibits a non-Abelian phase that is consistent with SU(2)_4 topological order, and can be accessed by gauging the \u2124_2 symmetry in the SET. Employing Levin-Wen string-net models with \u2124_2-graded structure, we generalize this picture to construct a large class of commuting-projector models for \u2124_2 SETs and non-Abelian topological orders exhibiting the same relation. Our construction provides the first commuting-projector-Hamiltonian realization of chiral bosonic non-Abelian topological order.", "doi": "10.1103/PhysRevB.97.245144", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2018-06-15", "series_number": "24", "volume": "97", "issue": "24", "pages": "Art. No. 245144" }, { "id": "authors:v2axr-0bv03", "collection": "authors", "collection_id": "v2axr-0bv03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170525-150801314", "type": "article", "title": "Symmetry and duality in bosonization of two-dimensional Dirac fermions", "author": [ { "family_name": "Mross", "given_name": "David F.", "orcid": "0000-0002-6585-1469", "clpid": "Mross-D-F" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Motrunich", "given_name": "Olexei I.", "orcid": "0000-0001-8031-0022", "clpid": "Motrunich-Olexei" } ], "abstract": "Recent work on a family of boson-fermion mappings has emphasized the interplay of symmetry and duality: Phases related by a particle-vortex duality of bosons (fermions) are related by time-reversal symmetry in their fermionic (bosonic) formulation. We present exact mappings for a number of concrete models that make this property explicit on the operator level. We illustrate the approach with one- and two-dimensional quantum Ising models and then similarly explore the duality web of complex bosons and Dirac fermions in (2+1) dimensions. We generalize the latter to systems with long-range interactions and discover a continuous family of dualities embedding the previously studied cases.", "doi": "10.1103/PhysRevX.7.041016", "issn": "2160-3308", "publisher": "American Physical Society", "publication": "Physical Review X", "publication_date": "2017-10", "series_number": "4", "volume": "7", "issue": "4", "pages": "Art. No. 041016" }, { "id": "authors:4bjwq-a2g67", "collection": "authors", "collection_id": "4bjwq-a2g67", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170705-111144781", "type": "article", "title": "Approximating the Sachdev-Ye-Kitaev model with Majorana wires", "author": [ { "family_name": "Chew", "given_name": "Aaron", "orcid": "0000-0003-0448-6215", "clpid": "Chew-Aaron" }, { "family_name": "Essin", "given_name": "Andrew", "clpid": "Essin-A-M" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "The Sachdev-Ye-Kitaev (SYK) model describes a collection of randomly interacting Majorana fermions that exhibits profound connections to quantum chaos and black holes. We propose a solid-state implementation based on a quantum dot coupled to an array of topological superconducting wires hosting Majorana zero modes. Interactions and disorder intrinsic to the dot mediate the desired random Majorana couplings, while an approximate symmetry suppresses additional unwanted terms. We use random-matrix theory and numerics to show that our setup emulates the SYK model (up to corrections that we quantify) and discuss experimental signatures.", "doi": "10.1103/PhysRevB.96.121119", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2017-09-15", "series_number": "12", "volume": "96", "issue": "12", "pages": "Art. No. 121119" }, { "id": "authors:6zccb-05980", "collection": "authors", "collection_id": "6zccb-05980", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170621-103050950", "type": "article", "title": "Scalable designs for quasiparticle-poisoning-protected topological quantum computation with Majorana zero modes", "author": [ { "family_name": "Karzig", "given_name": "Torsten", "orcid": "0000-0003-0834-0547", "clpid": "Karzig-T" }, { "family_name": "Knapp", "given_name": "Christina", "orcid": "0000-0002-5982-8107", "clpid": "Knapp-Christina" }, { "family_name": "Lutchyn", "given_name": "Roman M.", "orcid": "0000-0002-0222-9728", "clpid": "Lutchyn-R-M" }, { "family_name": "Bonderson", "given_name": "Parsa", "clpid": "Bonderson-P" }, { "family_name": "Hastings", "given_name": "Matthew B.", "clpid": "Hastings-M-B" }, { "family_name": "Nayak", "given_name": "Chetan", "clpid": "Nayak-C" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Flensberg", "given_name": "Karsten", "orcid": "0000-0002-8311-0103", "clpid": "Flensberg-K" }, { "family_name": "Plugge", "given_name": "Stephan", "orcid": "0000-0002-4844-2030", "clpid": "Plugge-S" }, { "family_name": "Oreg", "given_name": "Yuval", "clpid": "Oreg-Y" }, { "family_name": "Marcus", "given_name": "Charles M.", "orcid": "0000-0003-2420-4692", "clpid": "Marcus-C-M" }, { "family_name": "Freedman", "given_name": "Michael H.", "clpid": "Freedman-M-H" } ], "abstract": "We present designs for scalable quantum computers composed of qubits encoded in aggregates of four or more Majorana zero modes, realized at the ends of topological superconducting wire segments that are assembled into superconducting islands with significant charging energy. Quantum information can be manipulated according to a measurement-only protocol, which is facilitated by tunable couplings between Majorana zero modes and nearby semiconductor quantum dots. Our proposed architecture designs have the following principal virtues: (1) the magnetic field can be aligned in the direction of all of the topological superconducting wires since they are all parallel; (2) topological T junctions are not used, obviating possible difficulties in their fabrication and utilization; (3) quasiparticle poisoning is abated by the charging energy; (4) Clifford operations are executed by a relatively standard measurement: detection of corrections to quantum dot energy, charge, or differential capacitance induced by quantum fluctuations; (5) it is compatible with strategies for producing good approximate magic states.", "doi": "10.1103/PhysRevB.95.235305", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2017-06-15", "series_number": "23", "volume": "95", "issue": "23", "pages": "Art. No. 235305" }, { "id": "authors:y8det-hsk98", "collection": "authors", "collection_id": "y8det-hsk98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190828-155408422", "type": "book_section", "title": "Milestones toward Majorana-based quantum computing\n (Conference Presentation)", "book_title": "Spintronics IX", "author": [ { "family_name": "Mishmash", "given_name": "Ryan V.", "clpid": "Mishmash-R-V" }, { "family_name": "Aasen", "given_name": "David", "orcid": "0000-0002-6552-488X", "clpid": "Aasen-D" }, { "family_name": "Hell", "given_name": "Michael", "clpid": "Hell-M" }, { "family_name": "Higginbotham", "given_name": "Andrew", "clpid": "Higginbotham-A-P" }, { "family_name": "Danon", "given_name": "Jeroen", "clpid": "Danon-J" }, { "family_name": "Leijnse", "given_name": "Martin", "clpid": "Leijnse-M" }, { "family_name": "Jespersen", "given_name": "Thomas S.", "clpid": "Jespersen-T-S" }, { "family_name": "Folk", "given_name": "Joshua A.", "clpid": "Folk-J-A" }, { "family_name": "Marcus", "given_name": "Charles M.", "orcid": "0000-0003-2420-4692", "clpid": "Marcus-C-M" }, { "family_name": "Flensberg", "given_name": "Karsten", "orcid": "0000-0002-8311-0103", "clpid": "Flensberg-K" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "contributor": [ { "family_name": "Drouhin", "given_name": "Henri-Jean", "clpid": "Drouhin-H-J" }, { "family_name": "Wegrowe", "given_name": "Jean-Eric", "clpid": "Wegrowe-J-E" }, { "family_name": "Razeghi", "given_name": "Manijeh", "clpid": "Razeghi-M" } ], "abstract": "We introduce a scheme for preparation, manipulation, and readout of Majorana zero modes in semiconducting wires with mesoscopic superconducting islands. Our approach synthesizes recent advances in materials growth with tools commonly used in quantum-dot experiments, including gate-control of tunnel barriers and Coulomb effects, charge sensing, and charge pumping. We outline a sequence of milestones interpolating between zero-mode detection and quantum computing that includes (1) detection of fusion rules for non-Abelian anyons using either proximal charge sensors or pumped current; (2) validation of a prototype topological qubit; and (3) demonstration of non-Abelian statistics by braiding in a branched geometry. The first two milestones require only a single wire with two islands, and additionally enable sensitive measurements of the system's excitation gap, quasiparticle poisoning rates, residual Majorana zero-mode splittings, and topological-qubit coherence times. These pre-braiding experiments can be adapted to other manipulation and readout schemes as well.", "doi": "10.1117/12.2241102", "isbn": "9781510602533", "publisher": "Society of Photo-Optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "2016-11-04", "pages": "Art. No. 99313L" }, { "id": "authors:y1hry-5yp75", "collection": "authors", "collection_id": "y1hry-5yp75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161012-165715323", "type": "article", "title": "Interaction effects in superconductor/quantum spin Hall devices: Universal transport signatures and fractional Coulomb blockade", "author": [ { "family_name": "Aasen", "given_name": "David", "orcid": "0000-0002-6552-488X", "clpid": "Aasen-D" }, { "family_name": "Lee", "given_name": "Shu-Ping", "clpid": "Lee-Shu-Ping" }, { "family_name": "Karzig", "given_name": "Torsten", "orcid": "0000-0003-0834-0547", "clpid": "Karzig-T" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Interfacing s-wave superconductors and quantum spin Hall edges produces time-reversal-invariant topological superconductivity of a type that cannot arise in strictly one-dimensional systems. With the aim of establishing sharp fingerprints of this phase, we use renormalization-group methods to extract universal transport characteristics of superconductor/quantum spin Hall heterostructures where the native edge states serve as leads. We determine scaling forms for the conductance through a grounded superconductor and show that the results depend sensitively on the interaction strength in the leads, the size of the superconducting region, and the presence or absence of time-reversal-breaking perturbations. We also study transport across a floating superconducting island isolated by magnetic barriers. Here, we predict e-periodic Coulomb-blockade peaks, as recently observed in nanowire devices [S. M. Albrecht et al., Nature (London) 531, 206 (2016)], with the added feature that the island can support fractional charge tunable via the relative orientation of the barrier magnetizations. As an interesting corollary, when the magnetic barriers arise from strong interactions at the edge that spontaneously break time-reversal symmetry, the Coulomb-blockade periodicity changes from e to e/2. These findings suggest several future experiments that probe unique characteristics of topological superconductivity at the quantum spin Hall edge.", "doi": "10.1103/PhysRevB.94.165113", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2016-10-15", "series_number": "16", "volume": "94", "issue": "16", "pages": "Art. No. 165113" }, { "id": "authors:yjxww-y4f49", "collection": "authors", "collection_id": "yjxww-y4f49", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160518-123950203", "type": "article", "title": "Bosonic Analogue of Dirac Composite Fermi Liquid", "author": [ { "family_name": "Mross", "given_name": "David F.", "orcid": "0000-0002-6585-1469", "clpid": "Mross-D-F" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Motrunich", "given_name": "Olexei I.", "orcid": "0000-0001-8031-0022", "clpid": "Motrunich-Olexei" } ], "abstract": "We introduce a particle-hole-symmetric metallic state of bosons in a magnetic field at odd-integer filling. This state hosts composite fermions whose energy dispersion features a quadratic band touching and corresponding 2\u03c0 Berry flux protected by particle-hole and discrete rotation symmetries. We also construct an alternative particle-hole symmetric state\u2014distinct in the presence of inversion symmetry\u2014without Berry flux. As in the Dirac composite Fermi liquid introduced by Son [Phys. Rev. X 5, 031027 (2015)], breaking particle-hole symmetry recovers the familiar Chern-Simons theory. We discuss realizations of this phase both in 2D and on bosonic topological insulator surfaces, as well as signatures in experiments and simulations.", "doi": "10.1103/PhysRevLett.117.136802", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2016-09-23", "series_number": "13", "volume": "117", "issue": "13", "pages": "Art. No. 136802" }, { "id": "authors:dgs6f-90762", "collection": "authors", "collection_id": "dgs6f-90762", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160622-173202206", "type": "article", "title": "Ising anyons in frustration-free Majorana-dimer models", "author": [ { "family_name": "Ware", "given_name": "Brayden", "clpid": "Ware-B" }, { "family_name": "Son", "given_name": "Jun Ho", "clpid": "Son-Jun-Ho" }, { "family_name": "Cheng", "given_name": "Meng", "clpid": "Cheng-Meng" }, { "family_name": "Mishmash", "given_name": "Ryan V.", "clpid": "Mishmash-R-V" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Bauer", "given_name": "Bela", "orcid": "0000-0001-9796-2115", "clpid": "Bauer-B" } ], "abstract": "Dimer models have long been a fruitful playground for understanding topological physics. Here, we introduce a class, termed Majorana-dimer models, wherein bosonic dimers are decorated with pairs of Majorana modes. We find that the simplest examples of such systems realize an intriguing, intrinsically fermionic phase of matter that can be viewed as the product of a chiral Ising theory, which hosts deconfined non-Abelian quasiparticles, and a topological p_x\u2212ip_y superconductor. While the bulk anyons are described by a single copy of the Ising theory, the edge remains fully gapped. Consequently, this phase can arise in exactly solvable, frustration-free models. We describe two parent Hamiltonians: one generalizes the well-known dimer model on the triangular lattice, while the other is most naturally understood as a model of decorated fluctuating loops on a honeycomb lattice. Using modular transformations, we show that the ground-state manifold of the latter model unambiguously exhibits all properties of the Ising\u00d7(p_x\u2212ip_y) theory. We also discuss generalizations with more than one Majorana mode per site, which realize phases related to Kitaev's 16-fold way in a similar fashion.", "doi": "10.1103/PhysRevB.94.115127", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2016-09-15", "series_number": "11", "volume": "94", "issue": "11", "pages": "Art. No. 115127" }, { "id": "authors:8vz1q-3tj40", "collection": "authors", "collection_id": "8vz1q-3tj40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160912-161200262", "type": "article", "title": "Tunable spin\u2013orbit coupling and symmetry-protected edge states in graphene/WS_2", "author": [ { "family_name": "Yang", "given_name": "Bowen", "clpid": "Yang-Bowen" }, { "family_name": "Tu", "given_name": "Min-Feng", "clpid": "Tu-Min-Feng" }, { "family_name": "Kim", "given_name": "Jeongwoo", "clpid": "Kim-Jeongwoo" }, { "family_name": "Wu", "given_name": "Yong", "clpid": "Wu-Yong" }, { "family_name": "Wang", "given_name": "Hui", "clpid": "Wang-Hui" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Wu", "given_name": "Ruqian", "clpid": "Wu-Ruqian" }, { "family_name": "Bockrath", "given_name": "Marc", "clpid": "Bockrath-M-W" }, { "family_name": "Shi", "given_name": "Jing", "clpid": "Shi-Jing" } ], "abstract": "We demonstrate clear weak anti-localization (WAL) effect arising from induced Rashba spin\u2013orbit coupling (SOC) in WS_2-covered single-layer and bilayer graphene devices. Contrary to the uncovered region of a shared single-layer graphene flake, WAL in WS_2-covered graphene occurs over a wide range of carrier densities on both electron and hole sides. At high carrier densities, we estimate the Rashba SOC relaxation rate to be ~0.2 ps^(-1) and show that it can be tuned by transverse electric fields. In addition to the Rashba SOC, we also predict the existence of a'valley-Zeeman' SOC from first-principles calculations. The interplay between these two SOC's can open a non-topological but interesting gap in graphene; in particular, zigzag boundaries host four sub-gap edge states protected by time-reversal and crystalline symmetries. The graphene/WS_2 system provides a possible platform for these novel edge states.", "doi": "10.1088/2053-1583/3/3/031012", "issn": "2053-1583", "publisher": "IOP Publishing", "publication": "2D Materials", "publication_date": "2016-09", "series_number": "3", "volume": "3", "issue": "3", "pages": "Art. No. 031012" }, { "id": "authors:56wyf-c2c69", "collection": "authors", "collection_id": "56wyf-c2c69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160329-103533737", "type": "article", "title": "Milestones toward Majorana-based quantum computing", "author": [ { "family_name": "Aasen", "given_name": "David", "orcid": "0000-0002-6552-488X", "clpid": "Aasen-D" }, { "family_name": "Hell", "given_name": "Michael", "clpid": "Hell-M" }, { "family_name": "Mishmash", "given_name": "Ryan V.", "clpid": "Mishmash-R-V" }, { "family_name": "Higginbotham", "given_name": "Andrew", "clpid": "Higginbotham-A-P" }, { "family_name": "Danon", "given_name": "Jeroen", "clpid": "Danon-J" }, { "family_name": "Leijnse", "given_name": "Martin", "clpid": "Leijnse-M" }, { "family_name": "Jespersen", "given_name": "Thomas S.", "clpid": "Jespersen-T-S" }, { "family_name": "Folk", "given_name": "Joshua A.", "clpid": "Folk-J-A" }, { "family_name": "Marcus", "given_name": "Charles M.", "orcid": "0000-0003-2420-4692", "clpid": "Marcus-C-M" }, { "family_name": "Flensberg", "given_name": "Karsten", "orcid": "0000-0002-8311-0103", "clpid": "Flensberg-K" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "We introduce a scheme for preparation, manipulation, and read out of Majorana zero modes in semiconducting wires with mesoscopic superconducting islands. Our approach synthesizes recent advances in materials growth with tools commonly used in quantum-dot experiments, including gate control of tunnel barriers and Coulomb effects, charge sensing, and charge pumping. We outline a sequence of milestones interpolating between zero-mode detection and quantum computing that includes (1) detection of fusion rules for non-Abelian anyons using either proximal charge sensors or pumped current, (2) validation of a prototype topological qubit, and (3) demonstration of non-Abelian statistics by braiding in a branched geometry. The first two milestones require only a single wire with two islands, and additionally enable sensitive measurements of the system's excitation gap, quasiparticle poisoning rates, residual Majorana zero-mode splittings, and topological-qubit coherence times. These pre-braiding experiments can be adapted to other manipulation and read out schemes as well.", "doi": "10.1103/PhysRevX.6.031016", "issn": "2160-3308", "publisher": "American Physical Society", "publication": "Physical Review X", "publication_date": "2016-08", "series_number": "3", "volume": "6", "issue": "3", "pages": "Art. No. 031016" }, { "id": "authors:1t3yj-2k903", "collection": "authors", "collection_id": "1t3yj-2k903", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160510-085332659", "type": "article", "title": "Approaching a topological phase transition in Majorana nanowires", "author": [ { "family_name": "Mishmash", "given_name": "Ryan V.", "clpid": "Mishmash-R-V" }, { "family_name": "Aasen", "given_name": "David", "orcid": "0000-0002-6552-488X", "clpid": "Aasen-D" }, { "family_name": "Higginbotham", "given_name": "Andrew P.", "clpid": "Higginbotham-A-P" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Recent experiments have produced mounting evidence of Majorana zero modes in nanowire-superconductor hybrids. Signatures of an expected topological phase transition accompanying the onset of these modes nevertheless remain elusive. We investigate a fundamental question concerning this issue: Do well-formed Majorana modes necessarily entail a sharp phase transition in these setups? Assuming reasonable parameters, we argue that finite-size effects can dramatically smooth this putative transition into a crossover, even in systems large enough to support well-localized Majorana modes. We propose overcoming such finite-size effects by examining the behavior of low-lying excited states through tunneling spectroscopy. In particular, the excited-state energies exhibit characteristic field and density dependence, and scaling with system size, that expose an approaching topological phase transition. We suggest several experiments for extracting the predicted behavior. As a useful byproduct, the protocols also allow one to measure the wire's spin-orbit coupling directly in its superconducting environment.", "doi": "10.1103/PhysRevB.93.245404", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2016-06-15", "series_number": "24", "volume": "93", "issue": "24", "pages": "Art. No. 245404" }, { "id": "authors:t12sg-m7w03", "collection": "authors", "collection_id": "t12sg-m7w03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160404-083319765", "type": "article", "title": "Explicit derivation of duality between a free Dirac cone and quantum electrodynamics in (2+1) dimensions", "author": [ { "family_name": "Mross", "given_name": "David F.", "orcid": "0000-0002-6585-1469", "clpid": "Mross-D-F" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Motrunich", "given_name": "Olexei I.", "orcid": "0000-0001-8031-0022", "clpid": "Motrunich-Olexei" } ], "abstract": "We explicitly derive the duality between a free electronic Dirac cone and quantum electrodynamics in (2+1) dimensions (QED_3) with N=1 fermion flavors. The duality proceeds via an exact, non-local mapping from electrons to dual fermions with long-range interactions encoded by an emergent gauge field. This mapping allows us to construct parent Hamiltonians for exotic topological-insulator surface phases, derive the particle-hole-symmetric field theory of a half-filled Landau level, and nontrivially constrain QED_3 scaling dimensions. We similarly establish duality between bosonic topological insulator surfaces and N=2 QED_3.", "doi": "10.1103/PhysRevLett.117.016802", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2016-06", "series_number": "1", "volume": "117", "issue": "1", "pages": "Art. No. 016802" }, { "id": "authors:3gw58-qk072", "collection": "authors", "collection_id": "3gw58-qk072", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160315-085126670", "type": "article", "title": "Superconductors: Exponential boost for quantum information", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Quantum computers will one day wildly outperform conventional machines. An experimental feat reveals a fundamental property of exotic superconductors that brings this quantum technology a step closer.", "doi": "10.1038/531177a", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2016-03-09", "series_number": "7593", "volume": "531", "issue": "7593", "pages": "177-178" }, { "id": "authors:9gc0z-n0c29", "collection": "authors", "collection_id": "9gc0z-n0c29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160328-101600140", "type": "article", "title": "Topological Phases with Parafermions: Theory and Blueprints", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Fendley", "given_name": "Paul", "clpid": "Fendley-P" } ], "abstract": "We concisely review the recent evolution in the study of parafermions\u2014exotic emergent excitations that generalize Majorana fermions and similarly underpin a host of novel phenomena. First we generalize the intimate connection between the Z_2-symmetric Ising quantum spin chain and Majorana fermions to Z_3-symmetric chains and parafermions. In particular, we highlight how parafermion chains host a topological phase featuring protected edge zero modes. We then tour several blueprints for the laboratory realization of parafermion zero modes\u2014focusing on quantum Hall/superconductor hybrids, quantum Hall bilayers, and two-dimensional topological insulators\u2014and describe striking experimental fingerprints that they provide. Finally, we discuss how coupled parafermion arrays in quantum Hall architectures yield topological phases that potentially furnish hardware for a universal, intrinsically decoherence-free quantum computer.", "doi": "10.1146/annurev-conmatphys-031115-011336", "issn": "1947-5454", "publisher": "Annual Reviews", "publication": "Annual Review of Condensed Matter Physics", "publication_date": "2016-03", "volume": "7", "pages": "119-139" }, { "id": "authors:hvw2r-4xa26", "collection": "authors", "collection_id": "hvw2r-4xa26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151005-090948368", "type": "article", "title": "Anomalous Quasiparticle Symmetries and Non-Abelian Defects on Symmetrically Gapped Surfaces of Weak Topological Insulators", "author": [ { "family_name": "Mross", "given_name": "David F.", "orcid": "0000-0002-6585-1469", "clpid": "Mross-D-F" }, { "family_name": "Essin", "given_name": "Andrew", "clpid": "Essin-A-M" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Stern", "given_name": "Ady", "orcid": "0000-0002-9493-268X", "clpid": "Stern-Ady" } ], "abstract": "We show that boundaries of 3D weak topological insulators can become gapped by strong interactions while preserving all symmetries, leading to Abelian surface topological order. The anomalous nature of weak topological insulator surfaces manifests itself in a nontrivial action of symmetries on the quasiparticles; most strikingly, translations change the anyon types in a manner impossible in strictly 2D systems with the same symmetry. As a further consequence, screw dislocations form non-Abelian defects that trap \u2124_4 parafermion zero modes.", "doi": "10.1103/PhysRevLett.116.036803", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2016-01-22", "series_number": "3", "volume": "116", "issue": "3", "pages": "Art. No. 036803" }, { "id": "authors:qzeey-zzq97", "collection": "authors", "collection_id": "qzeey-zzq97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141020-102518072", "type": "article", "title": "Designer non-Abelian anyon platforms: from Majorana to Fibonacci", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Stern", "given_name": "Ady", "orcid": "0000-0002-9493-268X", "clpid": "Stern-A" } ], "abstract": "The emergence of non-Abelian anyons from large collections of interacting elementary particles is a conceptually beautiful phenomenon with important ramifications for fault-tolerant quantum computing. Over the last few decades the field has evolved from a highly theoretical subject to an active experimental area, particularly following proposals for trapping non-Abelian anyons in 'engineered' structures built from well-understood components. In this short overview we briefly tour the impressive progress that has taken place in the quest for the simplest type of non-Abelian anyon---defects binding Majorana zero modes---and then turn to similar strategies for pursuing more exotic excitations. Specifically, we describe how interfacing simple quantum Hall systems with conventional superconductors yields 'parafermionic' generalizations of Majorana modes and even Fibonacci anyons---the latter enabling fully fault tolerant universal quantum computation. We structure our treatment in a manner that unifies these topics in a coherent way. The ideas synthesized here spotlight largely uncharted experimental territory in the field of quantum Hall physics that appears ripe for discovery.", "doi": "10.1088/0031-8949/2015/T164/014006", "issn": "0031-8949", "publisher": "IOP", "publication": "Physica Scripta", "publication_date": "2015-12", "series_number": "T164", "volume": "2015", "issue": "T164", "pages": "Art. No. 014006" }, { "id": "authors:98sff-40e88", "collection": "authors", "collection_id": "98sff-40e88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150625-130152181", "type": "article", "title": "Assembling Fibonacci anyons from a \u2124_3 parafermion lattice model", "author": [ { "family_name": "Stoudenmire", "given_name": "E. M.", "orcid": "0000-0003-3389-9692", "clpid": "Stoudenmire-E-M" }, { "family_name": "Clarke", "given_name": "David J.", "clpid": "Clarke-D-J" }, { "family_name": "Mong", "given_name": "Roger S. K.", "clpid": "Mong-Roger-S-K" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Recent concrete proposals suggest it is possible to engineer a two-dimensional bulk phase supporting non-Abelian Fibonacci anyons out of Abelian fractional quantum Hall systems. The low-energy degrees of freedom of such setups can be modeled as \u2124_3 parafermions \"hopping\" on a two-dimensional lattice. We use the density matrix renormalization group to study a model of this type interpolating between the decoupled-chain, triangular-lattice, and square-lattice limits. The results show clear evidence of the Fibonacci phase over a wide region of the phase diagram, most notably including the isotropic triangular-lattice point. We also study the broader phase diagram of this model and show that elsewhere it supports an Abelian state with semionic excitations.", "doi": "10.1103/PhysRevB.91.235112", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2015-06-15", "series_number": "23", "volume": "91", "issue": "23", "pages": "Art. No. 235112" }, { "id": "authors:v9ee8-wet30", "collection": "authors", "collection_id": "v9ee8-wet30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141102-090252701", "type": "article", "title": "Composite Dirac liquids: parent states for symmetric surface topological order", "author": [ { "family_name": "Mross", "given_name": "David F.", "orcid": "0000-0002-6585-1469", "clpid": "Mross-D-F" }, { "family_name": "Essin", "given_name": "Andrew", "clpid": "Essin-A-M" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "We introduce exotic gapless states\u2014\"composite Dirac liquids\"\u2014that can appear at a strongly interacting surface of a three-dimensional electronic topological insulator. Composite Dirac liquids exhibit a gap to all charge excitations but nevertheless feature a single massless Dirac cone built from emergent electrically neutral fermions. These states thus comprise electrical insulators that, interestingly, retain thermal properties similar to those of the noninteracting topological insulator surface. A variety of novel fully gapped phases naturally descend from composite Dirac liquids. Most remarkably, we show that gapping the neutral fermions via Cooper pairing\u2014which crucially does not violate charge conservation\u2014yields symmetric non-Abelian topologically ordered surface phases captured in several recent works. Other (Abelian) topological orders emerge upon alternatively gapping the neutral Dirac cone with magnetism. We establish a hierarchical relationship between these descendant phases and expose an appealing connection to paired states of composite Fermi liquids arising in the half filled Landau level of two-dimensional electron gases. To controllably access these states we exploit a quasi-1D deformation of the original electronic Dirac cone that enables us to analytically address the fate of the strongly interacting surface. The algorithm we develop applies quite broadly and further allows the construction of symmetric surface topological orders for recently introduced bosonic topological insulators.", "doi": "10.1103/PhysRevX.5.011011", "issn": "2160-3308", "publisher": "American Physical Society", "publication": "Physical Review X", "publication_date": "2015-02-05", "series_number": "1", "volume": "5", "issue": "1", "pages": "Art. No. 011011" }, { "id": "authors:93trp-s0452", "collection": "authors", "collection_id": "93trp-s0452", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-151726687", "type": "article", "title": "Parafermionic conformal field theory on the lattice", "author": [ { "family_name": "Mong", "given_name": "Roger S. K.", "clpid": "Mong-S-K" }, { "family_name": "Clarke", "given_name": "David J.", "clpid": "Clarke-D-J" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Lindner", "given_name": "Netanel H.", "orcid": "0000-0003-1879-3902", "clpid": "Lindner-N-H" }, { "family_name": "Fendley", "given_name": "Paul", "clpid": "Fendley-P" } ], "abstract": "Finding the precise correspondence between lattice operators and the continuum fields that describe their long-distance properties is a largely open problem for strongly interacting critical points. Here we solve this problem\nessentially completely in the case of the three-state Potts model, which\nexhibits a phase transition described by a strongly interacting 'parafermion' conformal field theory. Using symmetry arguments, insights from integrability, and extensive simulations, we construct lattice analogues of nearly all the\nrelevant and marginal physical fields governing this transition. This construction includes chiral fields such as the parafermion. Along the way we also clarify the structure of operator product expansions between order and disorder fields, which we confirm numerically. Our results both suggest a systematic methodology for attacking non-free field theories on the lattice and find broader applications in the pursuit of exotic topologically ordered phases\nof matter.", "doi": "10.1088/1751-8113/47/45/452001", "issn": "0305-4470", "publisher": "IOP", "publication": "Journal of Physics A: Mathematical and General", "publication_date": "2014-11-14", "series_number": "45", "volume": "47", "issue": "45", "pages": "Art. No. 452001" }, { "id": "authors:t14bt-nwk14", "collection": "authors", "collection_id": "t14bt-nwk14", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141218-113655042", "type": "article", "title": "Classification of spin liquids on the square lattice with strong spin-orbit coupling", "author": [ { "family_name": "Reuther", "given_name": "Johannes", "clpid": "Reuther-J" }, { "family_name": "Lee", "given_name": "Shu-Ping", "clpid": "Lee-S-P" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Spin liquids represent exotic types of quantum matter that evade conventional symmetry-breaking order even at zero temperature. Exhaustive classifications of spin liquids have been carried out in several systems, particularly in the presence of full SU(2) spin-rotation symmetry. Real magnetic compounds, however, generically break SU(2) spin symmetry as a result of spin-orbit coupling\u2014which in many materials provides an \"order one\" effect. We generalize previous works by using the projective symmetry group method to classify Z_2 spin liquids on the square lattice when SU(2) spin symmetry is maximally lifted. We find that, counterintuitively, the lifting of spin symmetry actually results in vastly more spin-liquid phases compared to SU(2)-invariant systems. A generic feature of the SU(2)-broken case is that the spinons naturally undergo p+ip pairing; consequently, many of these Z_2 spin liquids feature a topologically nontrivial spinon band structure supporting gapless Majorana edge states. We study in detail several spin-liquid phases with varying numbers of gapless edge states and discuss their topological protection. The edge states are often protected by a combination of time reversal and lattice symmetries and hence resemble recently proposed topological crystalline superconductors.", "doi": "10.1103/PhysRevB.90.174417", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2014-11-14", "series_number": "17", "volume": "90", "issue": "17", "pages": "Art. No. 174417" }, { "id": "authors:etjp7-b7375", "collection": "authors", "collection_id": "etjp7-b7375", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141212-134339628", "type": "article", "title": "Parafermionic conformal field theory on the lattice", "author": [ { "family_name": "Mong", "given_name": "Roger S. K.", "clpid": "Mong-R-S-K" }, { "family_name": "Clarke", "given_name": "David J.", "clpid": "Clarke-D-J" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Lindner", "given_name": "Netanel H.", "orcid": "0000-0003-1879-3902", "clpid": "Lindner-N-H" }, { "family_name": "Fendley", "given_name": "Paul", "clpid": "Fendley-P" } ], "abstract": "Finding the precise correspondence between lattice operators and the continuum fields that describe their long-distance properties is a largely open problem for strongly interacting critical points. Here, we solve this problem essentially completely in the case of the three-state Potts model, which exhibits a phase transition described by a strongly interacting 'parafermion' conformal field theory. Using symmetry arguments, insights from integrability, and extensive simulations, we construct lattice analogues of nearly all the relevant and marginal physical fields governing this transition. This construction includes chiral fields such as the parafermion. Along the way we also clarify the structure of operator product expansions between order and disorder fields, which we confirm numerically. Our results both suggest a systematic methodology for attacking non-free field theories on the lattice and find broader applications in the pursuit of exotic topologically ordered phases of matter.", "doi": "10.1088/1751-8113/47/45/452001", "issn": "1751-8113", "publisher": "IOP", "publication": "Journal of Physics A: Mathematical and Theoretical", "publication_date": "2014-11-14", "series_number": "45", "volume": "47", "issue": "45", "pages": "Art. No. 452001" }, { "id": "authors:nmpk2-1dr40", "collection": "authors", "collection_id": "nmpk2-1dr40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140409-130620943", "type": "article", "title": "Revealing topological superconductivity in extended quantum spin Hall Josephson junctions", "author": [ { "family_name": "Lee", "given_name": "Shu-Ping", "clpid": "Lee-S-P" }, { "family_name": "Michaeli", "given_name": "Karen", "clpid": "Michaeli-K" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Yacoby", "given_name": "Amir", "clpid": "Yacoby-A" } ], "abstract": "Quantum spin Hall\u2013superconductor hybrids are promising sources of topological superconductivity and Majorana modes, particularly given recent progress on HgTe and InAs/GaSb. We propose a new method of revealing topological superconductivity in extended quantum spin Hall Josephson junctions supporting \"fractional Josephson currents.\" Specifically, we show that as one threads magnetic flux between the superconductors, the critical current traces an interference pattern featuring sharp fingerprints of topological superconductivity\u2014even when noise spoils parity conservation.", "doi": "10.1103/PhysRevLett.113.197001", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2014-11-07", "series_number": "19", "volume": "113", "issue": "19", "pages": "Art. No. 197001" }, { "id": "authors:3psp7-1mq74", "collection": "authors", "collection_id": "3psp7-1mq74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140714-162510303", "type": "article", "title": "Exotic circuit elements from zero-modes in hybrid superconductor-quantum Hall systems", "author": [ { "family_name": "Clarke", "given_name": "David J.", "clpid": "Clarke-D-J" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Shtengel", "given_name": "Kirill", "clpid": "Shtengel-K" } ], "abstract": "The fractional quantum Hall effect and superconductivity, remarkable phenomena in their own right, can harbour even more\nexotic physics at their interface. In particular, coupling quantum Hall edges with a superconductor can create emergent\nexcitations known as non-Abelian anyons that trap widely coveted Majorana fermion zero-modes and generalizations thereof.\nWe uncover non-local transport signatures of these zero-modes that not only provide striking experimental signatures of the\nanyons, but moreover allow one to construct novel circuit elements, including superconducting current and voltage mirrors,\nfractional charge transistors and flux-based capacitors. Underlying this unusual transport is a phenomenon that we term\n'perfect Andreev conversion'\u2014whereby quasiparticles propagating chirally at the edge reverse their electric charge as a result\nof hybridization with the zero-modes. Our findings suggest numerous experimental directions in the study of quantum-Hall\u2013superconductor systems hybrids and highlight a fundamentally new application of non-Abelian anyons.", "doi": "10.1038/nphys3114", "issn": "1745-2473", "publisher": "Nature Publishing Group", "publication": "Nature Physics", "publication_date": "2014-11", "series_number": "11", "volume": "10", "issue": "11", "pages": "877-882" }, { "id": "authors:mj542-mfg37", "collection": "authors", "collection_id": "mj542-mfg37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141106-101230634", "type": "article", "title": "Stability of zero modes in parafermion chains", "author": [ { "family_name": "Jermyn", "given_name": "Adam S.", "orcid": "0000-0001-5048-9973", "clpid": "Jermyn-A-S" }, { "family_name": "Mong", "given_name": "Roger S. K.", "clpid": "Mong-Roger-S-K" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Fendley", "given_name": "Paul", "clpid": "Fendley-P" } ], "abstract": "One-dimensional topological phases can host localized zero-energy modes that enable high-fidelity storage and manipulation of quantum information. Majorana fermion chains support a classic example of such a phase, having zero modes that guarantee twofold degeneracy in all eigenstates up to exponentially small finite-size corrections. Chains of \"parafermions\"\u2014generalized Majorana fermions\u2014also support localized zero modes, but, curiously, only under much more restricted circumstances. We shed light on the enigmatic zero-mode stability in parafermion chains by analytically and numerically studying the spectrum and developing an intuitive physical picture in terms of domain-wall dynamics. Specifically, we show that even if the system resides in a gapped topological phase with an exponentially accurate ground-state degeneracy, higher-energy states can exhibit a splitting that scales as a power law with system size, categorically ruling out exact localized zero modes. The transition to power-law behavior is described by critical behavior appearing exclusively within excited states.", "doi": "10.1103/PhysRevB.90.165106", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2014-10-15", "series_number": "16", "volume": "90", "issue": "16", "pages": "Art. No. 165106" }, { "id": "authors:b4q8s-8cb92", "collection": "authors", "collection_id": "b4q8s-8cb92", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140421-104643131", "type": "article", "title": "Universal Topological Quantum Computation from a Superconductor-Abelian Quantum Hall Heterostructure", "author": [ { "family_name": "Mong", "given_name": "Roger S. K.", "clpid": "Mong-R-S-K" }, { "family_name": "Clarke", "given_name": "David J.", "clpid": "Clarke-D-J" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Lindner", "given_name": "Netanel H.", "orcid": "0000-0003-1879-3902", "clpid": "Lindner-N-H" }, { "family_name": "Fendley", "given_name": "Paul", "clpid": "Fendley-P" }, { "family_name": "Nayak", "given_name": "Chetan", "clpid": "Nayak-C" }, { "family_name": "Oreg", "given_name": "Yuval", "clpid": "Oreg-Y" }, { "family_name": "Stern", "given_name": "Ady", "orcid": "0000-0002-9493-268X", "clpid": "Stern-A" }, { "family_name": "Berg", "given_name": "Erez", "clpid": "Berg-E" }, { "family_name": "Shtengel", "given_name": "Kirill", "clpid": "Shtengel-K" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" } ], "abstract": "Non-Abelian anyons promise to reveal spectacular features of quantum mechanics that could ultimately provide the foundation for a decoherence-free quantum computer. A key breakthrough in the pursuit of these exotic particles originated from Read and Green's observation that the Moore-Read quantum Hall state and a (relatively simple) two-dimensional p+ip superconductor both support so-called Ising non-Abelian anyons. Here, we establish a similar correspondence between the Z_3 Read-Rezayi quantum Hall state and a novel two-dimensional superconductor in which charge-2e Cooper pairs are built from fractionalized quasiparticles. In particular, both phases harbor Fibonacci anyons that\u2014unlike Ising anyons\u2014allow for universal topological quantum computation solely through braiding. Using a variant of Teo and Kane's construction of non-Abelian phases from weakly coupled chains, we provide a blueprint for such a superconductor using Abelian quantum Hall states interlaced with an array of superconducting islands. Fibonacci anyons appear as neutral deconfined particles that lead to a twofold ground-state degeneracy on a torus. In contrast to a p+ip superconductor, vortices do not yield additional particle types, yet depending on nonuniversal energetics can serve as a trap for Fibonacci anyons. These results imply that one can, in principle, combine well-understood and widely available phases of matter to realize non-Abelian anyons with universal braid statistics. Numerous future directions are discussed, including speculations on alternative realizations with fewer experimental requirements.", "doi": "10.1103/PhysRevX.4.011036", "issn": "2160-3308", "publisher": "American Physical Society", "publication": "Physical Review X", "publication_date": "2014-03-12", "series_number": "1", "volume": "4", "issue": "1", "pages": "Art. No. 011036" }, { "id": "authors:93mj0-3af52", "collection": "authors", "collection_id": "93mj0-3af52", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131203-070612581", "type": "article", "title": "Magneto-Josephson effects and Majorana bound states in quantum wires", "author": [ { "family_name": "Pientka", "given_name": "Falko", "clpid": "Pientka-F" }, { "family_name": "Jiang", "given_name": "Liang", "orcid": "0000-0002-0000-9342", "clpid": "Jiang-Liang" }, { "family_name": "Pekker", "given_name": "David", "clpid": "Pekker-D" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Refael", "given_name": "Gil", "clpid": "Refael-G" }, { "family_name": "Oreg", "given_name": "Yuval", "clpid": "Oreg-Y" }, { "family_name": "von Oppen", "given_name": "Felix", "clpid": "von-Oppen-F" } ], "abstract": "A prominent signature of Majorana bound states is the exotic Josephson effects they produce, the classic example being a fractional Josephson current with 4\u03c0 periodicity in the phase difference across the junction. Recent work established that topological insulator edges support a novel 'magneto-Josephson effect', whereby a dissipationless current exhibits 4\u03c0-periodic dependence also on the relative orientation of the Zeeman fields in the two banks of the junction. Here, we explore the magneto-Josephson effect in junctions based on spin\u2013orbit-coupled quantum wires. In contrast to the topological insulator case, the periodicities of the magneto-Josephson effect no longer follow from an exact superconductor\u2013magnetism duality of the Hamiltonian. We employ numerical calculations as well as analytical arguments to identify the domain configurations that display exotic Josephson physics for quantum-wire junctions, and elucidate the characteristic differences with the corresponding setups for topological insulators edges. To provide guidance to experiments, we also estimate the magnitude of the magneto-Josephson effects in realistic parameter regimes, and compare the Majorana-related contribution to the coexisting 2\u03c0-periodic effects emerging from non-Majorana states.", "doi": "10.1088/1367-2630/15/11/115001", "issn": "1367-2630", "publisher": "IOP", "publication": "New Journal of Physics", "publication_date": "2013-11-01", "volume": "15", "pages": "Art. No. 115001" }, { "id": "authors:2brap-98329", "collection": "authors", "collection_id": "2brap-98329", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131010-112231019", "type": "article", "title": "Majorana modes materialize", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Condensed-matter physicists are steadily closing in on exotic excitations known as Majorana modes that could\nadvance both fundamental science and quantum computing.", "doi": "10.1038/nnano.2013.178", "issn": "1748-3387", "publisher": "Nature Publishing Group", "publication": "Nature Nanotechnology", "publication_date": "2013-09", "series_number": "9", "volume": "8", "issue": "9", "pages": "623-624" }, { "id": "authors:4ajkg-paj45", "collection": "authors", "collection_id": "4ajkg-paj45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130408-095618952", "type": "article", "title": "Gate defined wires in HgTe quantum wells: from Majorana fermions to spintronics", "author": [ { "family_name": "Reuther", "given_name": "Johannes", "clpid": "Reuther-J" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Yacoby", "given_name": "Amir", "clpid": "Yacoby-A" } ], "abstract": "We introduce a promising new platform for Majorana zero-modes and various spintronics applications based on gate-defined wires in HgTe quantum wells. Due to the Dirac-like band structure for HgTe the physics of such systems differs markedly from that of conventional quantum wires. Most strikingly, we show that the subband parameters for gate-defined HgTe wires exhibit exquisite tunability: modest gate voltage variation allows one to modulate the Rashba spin-orbit energies from zero up to ~30K, and the effective g-factors from zero up to giant values exceeding 600. The large achievable spin-orbit coupling and g-factors together allow one to access Majorana modes in this setting at exceptionally low magnetic fields while maintaining robustness against disorder. As an additional benefit, gate-defined wires (in HgTe or other settings) should greatly facilitate the fabrication of networks for refined transport experiments used to detect Majoranas, as well as the realization of non-Abelian statistics and quantum information devices.", "doi": "10.1103/PhysRevX.3.031011", "issn": "2160-3308", "publisher": "American Physical Society", "publication": "Physical Review X", "publication_date": "2013-08-26", "series_number": "3", "volume": "3", "issue": "3", "pages": "Art. No. 031011" }, { "id": "authors:9g9zp-ar906", "collection": "authors", "collection_id": "9g9zp-ar906", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130326-135438324", "type": "article", "title": "Magneto-Josephson effects in junctions with Majorana bound states", "author": [ { "family_name": "Jiang", "given_name": "Liang", "orcid": "0000-0002-0000-9342", "clpid": "Jiang-Liang" }, { "family_name": "Pekker", "given_name": "David", "clpid": "Pekker-D" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Refael", "given_name": "Gil", "clpid": "Refael-G" }, { "family_name": "Oreg", "given_name": "Yuval", "clpid": "Oreg-Y" }, { "family_name": "Brataas", "given_name": "Arne", "clpid": "Brataas-A" }, { "family_name": "von Oppen", "given_name": "Felix", "clpid": "von-Oppen-F" } ], "abstract": "We investigate 1D quantum systems that support Majorana bound states at interfaces between topologically distinct regions. In particular, we show that there exists a duality between particle-hole and spin degrees of freedom in certain spin-orbit-coupled 1D platforms such as topological insulator edges. This duality results in a spin analog of previously explored \"fractional Josephson effects\"\u2014that is, the spin current flowing across a magnetic junction exhibits 4\u03c0 periodicity in the relative magnetic field angle across the junction. Furthermore, the interplay between the particle-hole and spin degrees of freedom results in unconventional magneto-Josephson effects, such that the Josephson charge current is a function of the magnetic field orientation with periodicity 4\u03c0.", "doi": "10.1103/PhysRevB.87.075438", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2013-02-25", "series_number": "7", "volume": "87", "issue": "7", "pages": "Art. No. 075438" }, { "id": "authors:0tqab-spa32", "collection": "authors", "collection_id": "0tqab-spa32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130425-094630281", "type": "article", "title": "Exotic non-Abelian anyons from conventional fractional quantum Hall states", "author": [ { "family_name": "Clarke", "given_name": "David J.", "clpid": "Clarke-D-J" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Shtengel", "given_name": "Kirill", "clpid": "Shtengel-K" } ], "abstract": "Non-Abelian anyons\u2014particles whose exchange noncommutatively transforms a system's quantum state\u2014are widely sought for the exotic fundamental physics they harbour and for quantum computing applications. Numerous blueprints now exist for stabilizing the simplest type of non-Abelian anyon, defects binding Majorana modes, by interfacing widely available materials. Here we introduce a device fabricated from conventional fractional quantum Hall states and s-wave superconductors that supports exotic non-Abelian defects binding parafermionic zero modes, which generalize Majorana bound states. We show that these new modes can be experimentally identified (and distinguished from Majoranas) using Josephson measurements. We also provide a practical recipe for braiding parafermionic zero modes and show that they give rise to non-Abelian statistics. Interestingly, braiding in our setup produces a richer set of topologically protected operations when compared with the Majorana case. As a byproduct, we establish a new, experimentally realistic Majorana platform in weakly spin\u2013orbit-coupled materials such as gallium arsenide.", "doi": "10.1038/ncomms2340", "issn": "2041-1723", "publisher": "Nature Publishing Group", "publication": "Nature Communications", "publication_date": "2013-01", "volume": "4", "pages": "Art. No. 1348" }, { "id": "authors:0y653-mhw40", "collection": "authors", "collection_id": "0y653-mhw40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130201-101614553", "type": "article", "title": "Giant Topological Insulator Gap in Graphene with 5d Adatoms", "author": [ { "family_name": "Hu", "given_name": "Jun", "clpid": "Hu-Jun" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Wu", "given_name": "Ruqian", "clpid": "Wu-Ruqian" }, { "family_name": "Franz", "given_name": "Marcel", "clpid": "Franz-M" } ], "abstract": "Two-dimensional topological insulators (2D TIs) have been proposed as platforms for many intriguing applications, ranging from spintronics to topological quantum information processing. Realizing this potential will likely be facilitated by the discovery of new, easily manufactured materials in this class. With this goal in mind, we introduce a new framework for engineering a 2D TI by hybridizing graphene with impurity bands arising from heavy adatoms possessing partially filled d shells, in particular, osmium and iridium. First-principles calculations predict that the gaps generated by this means exceed 0.2 eV over a broad range of adatom coverage; moreover, tuning of the Fermi level is not required to enter the TI state. The mechanism at work is expected to be rather general and may open the door to designing new TI phases in many materials.", "doi": "10.1103/PhysRevLett.109.266801", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2012-12-27", "series_number": "26", "volume": "109", "issue": "26", "pages": "Art. No. 266801" }, { "id": "authors:yw3zj-jc791", "collection": "authors", "collection_id": "yw3zj-jc791", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121101-101619309", "type": "article", "title": "Electrical Manipulation of Majorana Fermions in an Interdigitated Superconductor-Ferromagnet Device", "author": [ { "family_name": "Lee", "given_name": "Shu-Ping", "clpid": "Lee-Shu-Ping" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Refael", "given_name": "Gil", "clpid": "Refael-G" } ], "abstract": "We show that a topological phase supporting Majorana fermions can form in a two-dimensional electron gas (2DEG) adjacent to an interdigitated superconductor-ferromagnet structure. An advantage of this setup is that the 2DEG can induce the required Zeeman splitting and superconductivity from a single interface, allowing one to utilize a wide class of 2DEGs including the surface states of bulk InAs. We demonstrate that the interdigitated device supports a robust topological phase when the finger spacing \u03bb is smaller than half of the Fermi wavelength \u03bb_F. In this regime, the electrons effectively see a \"smeared\" Zeeman splitting and pairing field despite the interdigitation. The topological phase survives even in the opposite limit \u03bb>\u03bb_F/2, although with a reduced bulk gap. We describe how to electrically generate a vortex in this setup to trap a Majorana mode, and predict an anomalous Fraunhofer pattern that provides a sharp signature of chiral Majorana edge states.", "doi": "10.1103/PhysRevLett.109.126403", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2012-09-18", "series_number": "12", "volume": "109", "issue": "12", "pages": "Art. No. 126403" }, { "id": "authors:rjtcv-ymd89", "collection": "authors", "collection_id": "rjtcv-ymd89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200225-123400150", "type": "article", "title": "New directions in the pursuit of Majorana fermions in solid state systems", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "The 1937 theoretical discovery of Majorana fermions\u2014whose defining property is that they are their own anti-particles\u2014has since impacted diverse problems ranging from neutrino physics and dark matter searches to the fractional quantum Hall effect and superconductivity. Despite this long history the unambiguous observation of Majorana fermions nevertheless remains an outstanding goal. This review paper highlights recent advances in the condensed matter search for Majorana that have led many in the field to believe that this quest may soon bear fruit. We begin by introducing in some detail exotic 'topological' one- and two-dimensional superconductors that support Majorana fermions at their boundaries and at vortices. We then turn to one of the key insights that arose during the past few years; namely, that it is possible to 'engineer' such exotic superconductors in the laboratory by forming appropriate heterostructures with ordinary s-wave superconductors. Numerous proposals of this type are discussed, based on diverse materials such as topological insulators, conventional semiconductors, ferromagnetic metals and many others. The all-important question of how one experimentally detects Majorana fermions in these setups is then addressed. We focus on three classes of measurements that provide smoking-gun Majorana signatures: tunneling, Josephson effects and interferometry. Finally, we discuss the most remarkable properties of condensed matter Majorana fermions\u2014the non-Abelian exchange statistics that they generate and their associated potential for quantum computation.", "doi": "10.1088/0034-4885/75/7/076501", "issn": "0034-4885", "publisher": "IOP", "publication": "Reports on Progress in Physics", "publication_date": "2012-07", "series_number": "7", "volume": "75", "issue": "7", "pages": "Art. No. 076501" }, { "id": "authors:qpkba-sch90", "collection": "authors", "collection_id": "qpkba-sch90", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120716-103347564", "type": "article", "title": "Universal transport signatures of Majorana fermions in superconductor-Luttinger liquid junctions", "author": [ { "family_name": "Fidkowski", "given_name": "Lukasz", "clpid": "Fidkowski-L" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Lindner", "given_name": "Netanel H.", "orcid": "0000-0003-1879-3902", "clpid": "Lindner-N-H" }, { "family_name": "Lutchyn", "given_name": "Roman M.", "orcid": "0000-0002-0222-9728", "clpid": "Lutchyn-R-M" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" } ], "abstract": "One of the most promising proposals for engineering topological superconductivity and Majorana fermions employs a spin-orbit coupled nanowire subjected to a magnetic field and proximate to an s-wave superconductor. When only part of the wire's length contacts to the superconductor, the remaining conducting portion serves as a natural lead that can be used to probe these Majorana modes via tunneling. The enhanced role of interactions in one dimension dictates that this configuration should be viewed as a superconductor-Luttinger liquid junction. We investigate such junctions between both helical and spinful Luttinger liquids, and topological as well as nontopological superconductors. We determine the phase diagram for each case and show that universal low-energy transport in these systems is governed by fixed points describing either perfect normal reflection or perfect Andreev reflection. In addition to capturing (in some instances) the familiar Majorana-mediated \"zero-bias anomaly\" in a new framework, we show that interactions yield dramatic consequences in certain regimes. Indeed, we establish that strong repulsion removes this conductance anomaly altogether while strong attraction produces dynamically generated effective Majorana modes even in a junction with a trivial superconductor. Interactions further lead to striking signatures in the local density of states and the line shape of the conductance peak at finite voltage, and also are essential for establishing smoking-gun transport signatures of Majorana fermions in spinful Luttinger liquid junctions.", "doi": "10.1103/PhysRevB.85.245121", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2012-06-19", "series_number": "24", "volume": "85", "issue": "24", "pages": "Art. No. 245121" }, { "id": "authors:jzgnz-mg350", "collection": "authors", "collection_id": "jzgnz-mg350", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120502-145534850", "type": "article", "title": "Adiabatic manipulations of Majorana fermions in a three-dimensional network of quantum wires", "author": [ { "family_name": "Halperin", "given_name": "Bertrand I.", "orcid": "0000-0002-6999-1039", "clpid": "Halperin-B-I" }, { "family_name": "Oreg", "given_name": "Yuval", "clpid": "Oreg-Y" }, { "family_name": "Stern", "given_name": "Ady", "orcid": "0000-0002-9493-268X", "clpid": "Stern-A" }, { "family_name": "Refael", "given_name": "Gil", "clpid": "Refael-G" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "von Oppen", "given_name": "Felix", "clpid": "von-Oppen-F" } ], "abstract": "It has been proposed that localized zero-energy Majorana states can be realized in a two-dimensional network of quasi-one-dimensional semiconductor wires that are proximity coupled to a bulk superconductor. The wires should have strong spin-orbit coupling with appropriate symmetry, and their electrons should be partially polarized by a strong Zeeman field. Then, if the Fermi level is in an appropriate range, the wire can be in a topological superconducting phase, with Majorana states that occur at wire ends and at Y junctions, where three topological superconductor segments may be joined. Here we generalize these ideas to consider a three-dimensional network. The positions of Majorana states can be manipulated, and their non-Abelian properties made visible, by using external gates to selectively deplete portions of the network or by physically connecting and redividing wire segments. Majorana states can also be manipulated by reorientations of the Zeeman field on a wire segment, by physically rotating the wire about almost any axis, or by evolution of the phase of the order parameter in the proximity-coupled superconductor. We show how to keep track of sign changes in the zero-energy Hilbert space during adiabatic manipulations by monitoring the evolution of each Majorana state separately, rather than keeping track of the braiding of all possible pairs. This has conceptual advantages in the case of a three-dimensional network, and may be computationally useful even in two dimensions, if large numbers of Majorana sites are involved.", "doi": "10.1103/PhysRevB.85.144501", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2012-04-02", "series_number": "14", "volume": "85", "issue": "14", "pages": "Art. No. 144501" }, { "id": "authors:yvkvs-3n480", "collection": "authors", "collection_id": "yvkvs-3n480", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120206-102258105", "type": "article", "title": "Manipulating Majorana fermions using supercurrents", "author": [ { "family_name": "Romito", "given_name": "Alessandro", "clpid": "Romito-A" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Refael", "given_name": "Gil", "clpid": "Refael-G" }, { "family_name": "von Oppen", "given_name": "Felix", "clpid": "von-Oppen-F" } ], "abstract": "Topological insulator edges and spin-orbit-coupled quantum wires in proximity to s-wave superconductors can be tuned through a topological quantum phase transition by a Zeeman field. Here we show that a supercurrent flowing in the s-wave superconductor also drives such a transition. We propose to use this mechanism to generate and manipulate Majorana fermions that localize at domain walls between topological and nontopological regions of an edge or wire. In quantum wires, this method carries the added benefit that a supercurrent reduces the critical Zeeman field at which the topological phase appears.", "doi": "10.1103/PhysRevB.85.020502", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2012-01-06", "series_number": "2", "volume": "85", "issue": "2", "pages": "020502" }, { "id": "authors:87rq0-qwp97", "collection": "authors", "collection_id": "87rq0-qwp97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120131-101458254", "type": "article", "title": "Deformed triangular lattice antiferromagnets in a magnetic field: Role of spatial anisotropy and Dzyaloshinskii-Moriya interactions", "author": [ { "family_name": "Griset", "given_name": "Christian", "clpid": "Griset-C-D" }, { "family_name": "Head", "given_name": "Shane", "clpid": "Head-S" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Starykh", "given_name": "Oleg A.", "clpid": "Starykh-O-A" } ], "abstract": "Recent experiments on the anisotropic spin-1/2 triangular antiferromagnet Cs_2CuBr_4 have revealed a remarkably rich phase diagram in applied magnetic fields, consisting of an unexpectedly large number of ordered phases. Motivated by this finding, we study the role of three ingredients\u2014spatial anisotropy, Dzyaloshinskii-Moriya interactions, and quantum fluctuations\u2014on the magnetization process of a triangular antiferromagnet, coming from the semiclassical limit. The richness of the problem stems from two key facts: (1) the classical isotropic model with a magnetic field exhibits a large accidental ground-state degeneracy and (2) these three ingredients compete with one another and split this degeneracy in opposing ways. Using a variety of complementary approaches, including extensive Monte Carlo numerics, spin-wave theory, and an analysis of Bose-Einstein condensation of magnons at high fields, we find that their interplay gives rise to a complex phase diagram consisting of numerous incommensurate and commensurate phases. Our results shed light on the observed phase diagram for Cs_2CuBr_4 and suggest a number of future theoretical and experimental directions that will be useful for obtaining a complete understanding of this material's interesting phenomenology.", "doi": "10.1103/PhysRevB.84.245108", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2011-12-12", "series_number": "24", "volume": "84", "issue": "24", "pages": "Art. No. 245108" }, { "id": "authors:cxmwp-zsg75", "collection": "authors", "collection_id": "cxmwp-zsg75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120104-113454842", "type": "article", "title": "Unconventional Josephson Signatures of Majorana Bound States", "author": [ { "family_name": "Jiang", "given_name": "Liang", "orcid": "0000-0002-0000-9342", "clpid": "Jiang-Liang" }, { "family_name": "Pekker", "given_name": "David", "clpid": "Pekker-D" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Refael", "given_name": "Gil", "clpid": "Refael-G" }, { "family_name": "Oreg", "given_name": "Yuval", "clpid": "Oreg-Y" }, { "family_name": "von Oppen", "given_name": "Felix", "clpid": "von-Oppen-F" } ], "abstract": "A junction between two topological superconductors containing a pair of Majorana fermions exhibits a \"fractional\" Josephson effect, 4\u03c0 periodic in the superconductors' phase difference. An additional fractional Josephson effect, however, arises when the Majorana fermions are spatially separated by a superconducting barrier. This new term gives rise to a set of Shapiro steps which are essentially absent without Majorana modes and therefore provides a unique signature for these exotic states.", "doi": "10.1103/PhysRevLett.107.236401", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2011-11-28", "series_number": "23", "volume": "107", "issue": "23", "pages": "236401" }, { "id": "authors:t0wej-97h51", "collection": "authors", "collection_id": "t0wej-97h51", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110909-110431469", "type": "article", "title": "Impurity effects in highly frustrated diamond-lattice antiferromagnets", "author": [ { "family_name": "Savary", "given_name": "Lucile", "clpid": "Savary-Lucile" }, { "family_name": "Gull", "given_name": "Emanuel", "orcid": "0000-0002-6082-1260", "clpid": "Gull-Emanuel" }, { "family_name": "Trebst", "given_name": "Simon", "clpid": "Trebst-Simon" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Bergman", "given_name": "Doron", "clpid": "Bergman-Doron" }, { "family_name": "Balents", "given_name": "Leon", "clpid": "Balents-Leon" } ], "abstract": "We consider the effects of local impurities in highly frustrated diamond-lattice antiferromagnets, which exhibit large but nonextensive ground-state degeneracies. Such models are appropriate to many A-site magnetic spinels. We argue very generally that sufficiently dilute impurities induce an ordered magnetic ground state and provide a mechanism of degeneracy breaking. The states that are selected can be determined by a \"swiss cheese model\" analysis, which we demonstrate numerically for a particular impurity model in this case. Moreover, we present criteria for estimating the stability of the resulting ordered phase to a competing frozen (spin glass) one. The results may explain the contrasting finding of frozen and ordered ground states in CoAl_2O_4 and MnSc_2S_4, respectively.", "doi": "10.1103/PhysRevB.84.064438", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2011-08-29", "series_number": "6", "volume": "84", "issue": "6", "pages": "Art. No. 064438" }, { "id": "authors:xx7gb-zx620", "collection": "authors", "collection_id": "xx7gb-zx620", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200225-123359964", "type": "article", "title": "Interaction effects in topological superconducting wires supporting Majorana fermions", "author": [ { "family_name": "Stoudenmire", "given_name": "E. M.", "orcid": "0000-0003-3389-9692", "clpid": "Stoudenmire-E-M" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Starykh", "given_name": "Oleg A.", "clpid": "Starykh-O-A" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" } ], "abstract": "Among the broad spectrum of systems predicted to exhibit topological superconductivity and Majorana fermions, one-dimensional wires with strong spin-orbit coupling provide one of the most promising experimental candidates. Here we investigate the fate of the topological superconducting phase in such wires when repulsive interactions are present. Using a combination of density matrix renormalization group, bosonization, and Hartree\u2013Fock techniques, we demonstrate that while interactions degrade the bulk gap\u2014consistent with recent results of Gangadharaiah et al.\u2014they also greatly expand the parameter range over which the topological phase arises. In particular, we show that with interactions this phase can be accessed over a broader chemical potential window, thereby leading to greater immunity against disorder-induced chemical potential fluctuations in the wire. We also suggest that in certain wires strong interactions may allow Majorana fermions to be generated without requiring a magnetic field.", "doi": "10.1103/physrevb.84.014503", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2011-07-01", "series_number": "1", "volume": "84", "issue": "1", "pages": "Art. No. 014503" }, { "id": "authors:bqkpg-svp12", "collection": "authors", "collection_id": "bqkpg-svp12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110621-093218853", "type": "article", "title": "Majorana Fermions in Equilibrium and in Driven Cold-Atom Quantum Wires", "author": [ { "family_name": "Jiang", "given_name": "Liang", "orcid": "0000-0002-0000-9342", "clpid": "Jiang-Liang" }, { "family_name": "Kitagawa", "given_name": "Takuya", "clpid": "Kitagawa-Takuya" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Akhmerov", "given_name": "A. R.", "clpid": "Akhmerov-" }, { "family_name": "Pekker", "given_name": "David", "clpid": "Pekker-D" }, { "family_name": "Refael", "given_name": "Gil", "clpid": "Refael-G" }, { "family_name": "Cirac", "given_name": "J. Ignacio", "clpid": "Cirac-J-I" }, { "family_name": "Demler", "given_name": "Eugene", "clpid": "Demler-E-A" }, { "family_name": "Lukin", "given_name": "Mikhail D.", "orcid": "0000-0002-8658-1007", "clpid": "Lukin-M-D" }, { "family_name": "Zoller", "given_name": "Peter", "clpid": "Zoller-P" } ], "abstract": "We introduce a new approach to create and detect Majorana fermions using optically trapped 1D fermionic atoms. In our proposed setup, two internal states of the atoms couple via an optical Raman transition\u2014simultaneously inducing an effective spin-orbit interaction and magnetic field\u2014while a background molecular BEC cloud generates s-wave pairing for the atoms. The resulting cold-atom quantum wire supports Majorana fermions at phase boundaries between topologically trivial and nontrivial regions, as well as \"Floquet Majorana fermions\" when the system is periodically driven. We analyze experimental parameters, detection schemes, and various imperfections.", "doi": "10.1103/PhysRevLett.106.220402", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2011-06-02", "series_number": "22", "volume": "106", "issue": "22", "pages": "Art. No. 220402" }, { "id": "authors:cbske-gh304", "collection": "authors", "collection_id": "cbske-gh304", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110524-084153167", "type": "article", "title": "Non-Abelian statistics and topological quantum information processing in 1D wire networks", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Oreg", "given_name": "Yuval", "clpid": "Oreg-Y" }, { "family_name": "Refael", "given_name": "Gil", "clpid": "Refael-G" }, { "family_name": "von Oppen", "given_name": "Felix", "clpid": "von-Oppen-F" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" } ], "abstract": "The synthesis of a quantum computer remains an ongoing challenge in modern physics. Whereas decoherence stymies most approaches, topological quantum computation schemes evade decoherence at the hardware level by storing quantum information non-locally. Here we establish that a key operation\u2014braiding of non-Abelian anyons\u2014can be implemented using one-dimensional semiconducting wires. Such wires can be driven into a topological phase supporting long-sought particles known as Majorana fermions that can encode topological qubits. We show that in wire networks, Majorana fermions can be meaningfully braided by simply adjusting gate voltages, and that they exhibit non-Abelian statistics like vortices in a p+ip superconductor. We propose experimental set-ups that enable probing of the Majorana fusion rules and the efficient exchange of arbitrary numbers of Majorana fermions. This work should open a new direction in topological quantum computation that benefits from physical transparency and experimental feasibility.", "issn": "1745-2473", "publisher": "Nature Publishing Group", "publication": "Nature Physics", "publication_date": "2011-05", "series_number": "5", "volume": "7", "issue": "5", "pages": "412-417" }, { "id": "authors:s5y49-bpb05", "collection": "authors", "collection_id": "s5y49-bpb05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200225-105137997", "type": "monograph", "title": "Engineering a robust quantum spin Hall state in graphene via adatom deposition", "author": [ { "family_name": "Weeks", "given_name": "Conan", "clpid": "Weeks-C" }, { "family_name": "Hu", "given_name": "Jun", "clpid": "Hu-Jun" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Franz", "given_name": "Marcel", "clpid": "Franz-M" }, { "family_name": "Wu", "given_name": "Ruqian", "clpid": "Wu-Ruqian" } ], "abstract": "The 2007 discovery of quantized conductance in HgTe quantum wells delivered the field of topological insulators (TIs) its first experimental confirmation. While many three-dimensional TIs have since been identified, HgTe remains the only known two-dimensional system in this class. Difficulty fabricating HgTe quantum wells has, moreover, hampered their widespread use. With the goal of breaking this logjam we provide a blueprint for stabilizing a robust TI state in a more readily available two-dimensional material---graphene. Using symmetry arguments, density functional theory, and tight-binding simulations, we predict that graphene endowed with certain heavy adatoms realizes a TI with substantial band gap. For indium and thallium, our most promising adatom candidates, a modest 6% coverage produces an estimated gap near 80K and 240K, respectively, which should be detectable in transport or spectroscopic measurements. Engineering such a robust topological phase in graphene could pave the way for a new generation of devices for spintronics, ultra-low-dissipation electronics and quantum information processing.", "doi": "10.48550/arXiv.1104.3282", "publisher": "PHYS.REV.X", "publication_date": "2011-04-17" }, { "id": "authors:atmy7-qsg77", "collection": "authors", "collection_id": "atmy7-qsg77", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100513-142047300", "type": "article", "title": "Majorana fermions in a tunable semiconductor device", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "The experimental realization of Majorana fermions presents an important problem due to their non-Abelian nature and potential exploitation for topological quantum computation. Very recently Sau et al. [Phys. Rev. Lett. 104, 040502 (2010)] demonstrated that a topological superconducting phase supporting Majorana fermions can be realized using surprisingly conventional building blocks: a semiconductor quantum well coupled to an s-wave superconductor and a ferromagnetic insulator. Here we propose an alternative setup, wherein a topological superconducting phase is driven by applying an in-plane magnetic field to a (110)-grown semiconductor coupled only to an s-wave superconductor. This device offers a number of advantages, notably a simpler architecture and the ability to tune across a quantum phase transition into the topological superconducting state while still largely avoiding unwanted orbital effects. Experimental feasibility of both setups is discussed in some detail.", "doi": "10.1103/PhysRevB.81.125318", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2010-03", "series_number": "12", "volume": "81", "issue": "12", "pages": "Art. No. 125318" }, { "id": "authors:6sbfx-hf809", "collection": "authors", "collection_id": "6sbfx-hf809", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100114-143033701", "type": "article", "title": "Interlayer Coherent Composite Fermi Liquid Phase in Quantum Hall Bilayers", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Motrunich", "given_name": "Olexei I.", "orcid": "0000-0001-8031-0022", "clpid": "Motrunich-Olexei" }, { "family_name": "Refael", "given_name": "G.", "clpid": "Refael-G" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" } ], "abstract": "We introduce an interlayer coherent composite Fermi liquid for \u03bd=1/2+1/2 bilayers, in which interlayer Coulomb repulsion drives exciton condensation of composite fermions. As a result, composite fermions propagate coherently between layers\u2014even though electrons do not\u2014and form bonding and antibonding Fermi seas. This phase is compressible with respect to symmetric currents but quantum Hall-like in the counterflow channel. Quantum oscillations of the composite Fermi seas generate a new series of incompressible states at \u03bd=p/[2(p\u00b11)] per layer (p an integer), which is a bilayer analogue of Jain's sequence.", "doi": "10.1103/PhysRevLett.103.256403", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2009-12-18", "series_number": "25", "volume": "103", "issue": "25", "pages": "Art. No. 256403" }, { "id": "authors:12hkp-byr27", "collection": "authors", "collection_id": "12hkp-byr27", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090805-080211875", "type": "article", "title": "Bismuth in strong magnetic fields: unconventional Zeeman coupling and correlation effects", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Balents", "given_name": "Leon", "clpid": "Balents-L" } ], "abstract": "While the behavior of strongly interacting two-dimensional electrons in high magnetic fields is by now well understood, our understanding of the three-dimensional (3D) case is comparatively rudimentary. Illuminating this disparity are recent experiments on 3D bismuth, where unanticipated transport and magnetization structure\u2014including hysteresis\u2014persist even when all carriers are expected to reside in the lowest Landau level. Motivated by these findings, we derive a low-energy Hamiltonian for the hole and three Dirac electron pockets in bismuth which, crucially, encodes an unconventional Zeeman effect generated by spin-orbit coupling. We show that (1) this Zeeman coupling strongly suppresses the quantum limit for the Dirac electrons, giving rise to the observed magnetization structure, and (2) the hysteresis coincides with one of the pockets emptying its second Landau level, which is where Coulomb effects are most pronounced. Incorporating interactions, we find instabilities toward charge-density-wave and Wigner crystal phases and propose that hysteresis arises from a first-order transition out of the latter.", "doi": "10.1103/PhysRevB.79.241101", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2009-06-01", "series_number": "24", "volume": "79", "issue": "24", "pages": "Art. No. 241101" }, { "id": "authors:w3dxc-zh580", "collection": "authors", "collection_id": "w3dxc-zh580", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090630-100559408", "type": "article", "title": "Quantum stabilization of the 1/3-magnetization plateau in Cs_2CuBr_4", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Chubukov", "given_name": "Andrey V.", "clpid": "Chubukov-A-V" }, { "family_name": "Starykh", "given_name": "Oleg A.", "clpid": "Starykh-O-A" } ], "abstract": "We consider the phase diagram of a spatially anisotropic 2D triangular antiferromagnet in a magnetic field. Classically, the ground state is umbrellalike for all fields, but we show that the quantum phase diagram is much richer and contains a 1/3-magnetization plateau, two commensurate planar states, two incommensurate chiral umbrella phases, and, possibly, a spin density wave state separating the two chiral phases. Our analysis sheds light on several recent experimental findings for Cs_2CuBr_4.", "doi": "10.1103/PhysRevLett.102.137201", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2009-04-03", "series_number": "13", "volume": "102", "issue": "13", "pages": "137201" }, { "id": "authors:zxpn0-wvk34", "collection": "authors", "collection_id": "zxpn0-wvk34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ALIprb08", "type": "article", "title": "Monopole quantum numbers in the staggered flux spin liquid", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" } ], "abstract": "Algebraic spin liquids, which are exotic gapless spin states preserving all microscopic symmetries, have been widely studied due to potential realizations in frustrated quantum magnets and the cuprates. At low energies, such putative phases are described by quantum electrodynamics in 2+1 dimensions. While significant progress has been made in understanding this nontrivial interacting field theory and the associated spin physics, one important issue which has proved elusive is the quantum numbers carried by so-called monopole operators. Here we address this issue in the \"staggered flux\" spin liquid which may be relevant to the pseudogap regime in high Tc. Employing general analytical arguments supported by simple numerics, we argue that proximate phases encoded in the monopole operators include the familiar Neel and valence bond solid orders, as well as other symmetry-breaking orders closely related to those previously explored in the monopole-free sector of the theory. Surprisingly, we also find that one monopole operator carries trivial quantum numbers, and briefly discuss its possible implications.", "doi": "10.1103/PhysRevB.78.035126", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2008-07-15", "series_number": "3", "volume": "78", "issue": "3", "pages": "Art. No. 035126" }, { "id": "authors:kn9j1-jjp25", "collection": "authors", "collection_id": "kn9j1-jjp25", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200225-123400068", "type": "article", "title": "Interplay between lattice-scale physics and the quantum Hall effect in graphene", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" } ], "abstract": "Graphene's honeycomb lattice structure underlies much of the remarkable physics inherent in this material, most strikingly through the formation of two \"flavors\" of Dirac cones for each spin. In the quantum Hall regime, the resulting flavor degree of freedom leads to an interesting problem when a Landau level is partially occupied. Namely, while Zeeman splitting clearly favors polarizing spins along the field, precisely how the states for each flavor are occupied can become quite delicate. Here we focus on clean graphene sheets in the regime of quantum Hall ferromagnetism, and discuss how subtler lattice-scale physics, arising either from interactions or disorder, resolves this ambiguity to measurable consequence. Interestingly, such lattice-scale physics favors microscopic symmetry-breaking order coexisting with the usual liquid-like quantum Hall physics emerging on long length scales. The current experimental situation is briefly reviewed in light of our discussion.", "doi": "10.1016/j.ssc.2007.06.035", "issn": "0038-1098", "publisher": "Elsevier", "publication": "Solid State Communications", "publication_date": "2007-09", "series_number": "11-12", "volume": "143", "issue": "11-12", "pages": "504-509" }, { "id": "authors:0zftr-yh961", "collection": "authors", "collection_id": "0zftr-yh961", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200225-123359047", "type": "article", "title": "Order-by-disorder and spiral spin-liquid in frustrated diamond-lattice antiferromagnets", "author": [ { "family_name": "Bergman", "given_name": "Doron", "clpid": "Bergman-Doron-L" }, { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Gull", "given_name": "Emanuel", "orcid": "0000-0002-6082-1260", "clpid": "Gull-Emanuel" }, { "family_name": "Trebst", "given_name": "Simon", "clpid": "Trebst-Simon" }, { "family_name": "Balents", "given_name": "Leon", "clpid": "Balents-Leon" } ], "abstract": "Frustration refers to competition between different interactions that cannot be simultaneously satisfied\u2014a familiar feature in many magnetic solids. Strong frustration leads to highly degenerate ground states and a large suppression of ordering by fluctuations. Key challenges in frustrated magnetism include the characterization of the fluctuating spin-liquid regime and determination of the mechanism of eventual order at lower temperature. Here, we study a model of a diamond-lattice antiferromagnet appropriate for numerous spinel materials. With sufficiently strong frustration, a massive ground-state degeneracy develops amongst spirals whose propagation wavevectors reside on a continuous two-dimensional 'spiral surface' in momentum space. We argue that an important ordering mechanism is entropic splitting of the degenerate ground states, an elusive phenomenon called 'order by disorder'. A broad spiral spin-liquid regime emerges at higher temperatures, where the underlying spiral surface can be directly revealed through spin correlations. We discuss the agreement between these predictions and the well-characterized spinel MnSc\u2082S\u2084.", "doi": "10.1038/nphys622", "issn": "1745-2473", "publisher": "Nature Publishing Group", "publication": "Nature Physics", "publication_date": "2007-07", "series_number": "7", "volume": "3", "issue": "7", "pages": "487-491" }, { "id": "authors:rrk0z-yc692", "collection": "authors", "collection_id": "rrk0z-yc692", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:RYUprb07", "type": "article", "title": "Algebraic vortex liquid theory of a quantum antiferromagnet on the kagome lattice", "author": [ { "family_name": "Ryu", "given_name": "S.", "clpid": "Ryu-S" }, { "family_name": "Motrunich", "given_name": "O. I.", "orcid": "0000-0001-8031-0022", "clpid": "Motrunich-Olexei" }, { "family_name": "Alicea", "given_name": "J.", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" } ], "abstract": "There is growing evidence from both experiment and numerical studies that low half-odd integer quantum spins on a kagome lattice with predominant antiferromagnetic near-neighbor interactions do not order magnetically or break lattice symmetries even at temperatures much lower than the exchange interaction strength. Moreover, there appears to be a plethora of low-energy excitations, predominantly singlets but also spin carrying, which suggests that the putative underlying quantum spin liquid is a gapless \"critical spin liquid\" rather than a gapped spin liquid with topological order. Here, we develop an effective field theory approach for the spin-(1/2) Heisenberg model with easy-plane anisotropy on the kagome lattice. By employing a vortex duality transformation, followed by a fermionization and flux smearing, we obtain access to a gapless yet stable critical spin liquid phase, which is described by (2+1)-dimensional quantum electrodynamics (QED3) with an emergent SU(8) flavor symmetry. The specific heat, thermal conductivity, and dynamical structure factor are extracted from the effective field theory, and contrasted with other theoretical approaches to the kagome antiferromagnet.", "doi": "10.1103/PhysRevB.75.184406", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2007-05-01", "series_number": "18", "volume": "75", "issue": "18", "pages": "Art. No. 184406" }, { "id": "authors:h79wd-t9186", "collection": "authors", "collection_id": "h79wd-t9186", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200225-123359220", "type": "article", "title": "Critical spin liquid at \u2153 magnetization in a spin-\u00bd triangular antiferromagnet", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" } ], "abstract": "Although magnetically ordered at low temperatures, the spin-\u00bd triangular antiferromagnet Cs\u2082CuCl\u2084 exhibits remarkable spin dynamics that strongly suggest proximity to a spin-liquid phase. Here we ask whether a proximate spin liquid may also occur in an applied magnetic field, leaving a similar imprint on the dynamical spin correlations of this material. Specifically, we explore a spatially anisotropic Heisenberg spin-\u00bd triangular antiferromagnet at \u2153 magnetization from a dual vortex perspective, and indeed find a \"critical\" spin-liquid phase described by quantum electrodynamics in (2+1)-dimensions with an emergent SU(6) symmetry. A number of nontrivial predictions follow for the dynamical spin structure factor in this \"algebraic vortex liquid\" phase, which can be tested via inelastic neutron scattering. We also discuss how well-studied \"up-up-down\" magnetization plateaus can be captured within our approach, and further predict the existence of a stable gapless solid phase in a weakly ordered up-up-down state. Finally, we predict several anomalous \"roton\" minima in the excitation spectrum in the regime of lattice anisotropy where the canted N\u00e9el state appears.", "doi": "10.1103/physrevb.75.144411", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2007-04-01", "series_number": "14", "volume": "75", "issue": "14", "pages": "Art. No. 144411" }, { "id": "authors:d28df-awc04", "collection": "authors", "collection_id": "d28df-awc04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200225-123359309", "type": "article", "title": "Graphene integer quantum Hall effect in the ferromagnetic and paramagnetic regimes", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" } ], "abstract": "Starting from the graphene lattice tight-binding Hamiltonian with an on-site U and long-range Coulomb repulsion, we derive an interacting continuum Dirac theory governing the low-energy behavior of graphene in an applied magnetic field. Initially, we consider a clean graphene system within this effective theory and explore integer quantum Hall ferromagnetism stabilized by exchange from the long-range Coulomb repulsion. We study in detail the ground state and excitations at \u03bd=0 and \u03bd=\u00b11, taking into account small symmetry-breaking terms that arise from the lattice-scale interactions, and also explore the ground states selected at \u03bd=\u00b13, \u00b14, and \u00b15. We argue that the ferromagnetic regime may not yet be realized in current experimental samples, which at the above filling factors perhaps remain paramagnetic due to strong disorder. In an attempt to access the latter regime where the role of exchange is strongly suppressed by disorder, we apply Hartree theory to study the effects of interactions. Here, we find that Zeeman splitting together with symmetry-breaking interactions can in principle produce integer quantum Hall states in a paramagnetic system at \u03bd=0, \u00b11, and \u00b14, but not at \u03bd=\u00b13 or \u00b15, consistent with recent experiments in high magnetic fields. We make predictions for the activation energies in these quantum Hall states which will be useful for determining their true origin.", "doi": "10.1103/physrevb.74.075422", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2006-08-15", "series_number": "7", "volume": "74", "issue": "7", "pages": "Art. No. 075422" }, { "id": "authors:h774g-pw174", "collection": "authors", "collection_id": "h774g-pw174", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ALIprb06", "type": "article", "title": "Theory of the algebraic vortex liquid in an anisotropic spin-(1/2) triangular antiferromagnet", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Motrunich", "given_name": "Olexei I.", "orcid": "0000-0001-8031-0022", "clpid": "Motrunich-Olexei" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" } ], "abstract": "We explore spin-(1/2) triangular antiferromagnets with both easy-plane and lattice exchange anisotropies by employing a dual vortex mapping followed by a fermionization of the vortices. Over a broad range of exchange anisotropy, this approach leads naturally to a \"critical\" spin liquid\u2014the algebraic vortex liquid\u2014which appears to be distinct from other known spin liquids. We present a detailed characterization of this state, which is described in terms of noncompact QED3 with an emergent SU(4) symmetry. Descendant phases of the algebraic vortex liquid are also explored, which include the Kalmeyer-Laughlin spin liquid, a variety of magnetically ordered states such as the well-known coplanar spiral state, and supersolids. In the range of exchange anisotropy where the \"square lattice\" N\u00e9el ground state arises, we demonstrate that anomalous \"roton\" minima in the excitation spectrum recently reported in series expansions can be accounted for within our approach.", "doi": "10.1103/PhysRevB.73.174430", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2006-05-01", "series_number": "17", "volume": "73", "issue": "17", "pages": "Art. No. 174430" }, { "id": "authors:k4te2-v7j91", "collection": "authors", "collection_id": "k4te2-v7j91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ALIprl05", "type": "article", "title": "Algebraic Vortex Liquid in Spin-1/2 Triangular Antiferromagnets: Scenario for Cs2CuCl4", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Motrunich", "given_name": "Olexei I.", "orcid": "0000-0001-8031-0022", "clpid": "Motrunich-Olexei" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" } ], "abstract": "Motivated by inelastic neutron scattering data on Cs2CuCl4, we explore spin-1/2 triangular lattice antiferromagnets with both spatial and easy-plane exchange anisotropies, the latter due to an observed Dzyaloshinskii-Moriya interaction. Exploiting a duality mapping followed by a fermionization of the dual vortex degrees of freedom, we find a novel critical spin-liquid phase described in terms of Dirac fermions with an emergent global SU(4) symmetry minimally coupled to a noncompact U(1) gauge field. This \"algebraic vortex liquid\" supports gapless spin excitations and universal power-law correlations in the dynamical spin structure factor which are consistent with those observed in Cs2CuCl4. We suggest future neutron scattering experiments that should help distinguish between the algebraic vortex liquid and other spin liquids and quantum critical points previously proposed in the context of Cs2CuCl4.", "doi": "10.1103/PhysRevLett.95.247203", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2005-12-09", "series_number": "24", "volume": "95", "issue": "24", "pages": "Art. No. 247203" }, { "id": "authors:46cr9-s3274", "collection": "authors", "collection_id": "46cr9-s3274", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ALIprb05", "type": "article", "title": "Criticality in quantum triangular antiferromagnets via fermionized vortices", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Motrunich", "given_name": "Olexei I.", "orcid": "0000-0001-8031-0022", "clpid": "Motrunich-Olexei" }, { "family_name": "Hermele", "given_name": "Michael", "clpid": "Hermele-M" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" } ], "abstract": "We reexamine two-dimensional frustrated quantum magnetism with the aim of exploring new critical points and critical phases. We study easy-plane triangular antiferromagnets using a dual vortex approach, fermionizing the vortices with a Chern-Simons field. Herein we develop this technique for integer-spin systems which generically exhibit a simple paramagnetic phase as well as magnetically ordered phases with coplanar and collinear spin order. Within the fermionized-vortex approach, we derive a low-energy effective theory containing Dirac fermions with two flavors minimally coupled to a U(1) and a Chern-Simons gauge field. At criticality we argue that the Chern-Simons gauge field can be subsumed into the U(1) gauge field, and up to irrelevant interactions one arrives at quantum electrodynamics in 2+1 dimensions (QED3). Moreover, we conjecture that critical QED3 with full SU(2) flavor symmetry describes the O(4) multicritical point of the spin model where the paramagnet and two magnetically ordered phases merge. The remarkable implication is that QED3 with flavor SU(2) symmetry is dual to ordinary critical \u03a6^4 field theory with O(4) symmetry. This leads to a number of unexpected, verifiable predictions for QED3. A connection of our fermionized-vortex approach with the dipole interpretation of the nu=1/2 fractional quantum Hall state is also demonstrated. The approach introduced in this paper will be applied to spin-1/2 systems in a forthcoming publication.", "doi": "10.1103/PhysRevB.72.064407", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2005-08-01", "series_number": "6", "volume": "72", "issue": "6", "pages": "Art. No. 064407" }, { "id": "authors:zwtqf-hz834", "collection": "authors", "collection_id": "zwtqf-hz834", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200225-123359397", "type": "article", "title": "Transition to zero resistance in a two-dimensional electron gas driven with microwaves", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Balents", "given_name": "Leon", "clpid": "Balents-L" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" }, { "family_name": "Paramekanti", "given_name": "Arun", "clpid": "Paramekanti-A" }, { "family_name": "Radzihovsky", "given_name": "Leo", "orcid": "0000-0002-2281-0835", "clpid": "Radzihovsky-Leo" } ], "abstract": "High-mobility two-dimensional electron systems in a perpendicular magnetic field exhibit zero-resistance states (ZRSs) when driven with microwave radiation. We study the nonequilibrium phase transition into the ZRS using phenomenological equations of motion to describe the electron current and density fluctuations in the presence of a magnetic field. We focus on two models to describe the transition into a time-independent steady state. In model I the equations of motion are invariant under a global uniform change in the density. This model is argued to describe physics on small length scales where the density does not vary appreciably from its mean. The ordered state that arises in this case spontaneously breaks rotational invariance in the plane and consists of a uniform current and a transverse Hall field. We discuss some properties of this state, such as stability to fluctuations and the appearance of a Goldstone mode associated with the continuous symmetry breaking. Using dynamical renormalization group techniques, we find that with short-range interactions this model can admit a continuous transition described by mean-field theory, whereas with long-range interactions the transition is driven first order. In model II, we relax the invariance under global density shifts as appropriate for describing the system on longer length scales, and in this case we predict a first-order transition with either short- or long-range interactions. We discuss implications for experiments, including a possible way to detect the Goldstone mode in the ZRS, scaling relations expected to hold in the case of an apparent continuous transition into the ZRS, and a possible signature of a first-order transition in larger samples. Our framework for describing the phase transition into the ZRS also highlights the connection of this problem to the well-studied phenomenon of \"bird flocking.\"", "doi": "10.1103/physrevb.71.235322", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2005-06-15", "series_number": "23", "volume": "71", "issue": "23", "pages": "Art. No. 235322" }, { "id": "authors:4vfph-v9g61", "collection": "authors", "collection_id": "4vfph-v9g61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200225-123359485", "type": "article", "title": "Charge accumulation on a Luttinger liquid", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Bena", "given_name": "Cristina", "clpid": "Bena-Cristina" }, { "family_name": "Balents", "given_name": "Leon", "clpid": "Balents-L" }, { "family_name": "Fisher", "given_name": "Matthew P. A.", "clpid": "Fisher-Matthew-P-A" } ], "abstract": "The average charge Q on a quantum wire, modeled as a single-channel Luttinger liquid (LL), connected to metallic leads and coupled to a gate is studied theoretically. We find that the behavior of the charge as the gate voltage V_G varies depends strongly on experimentally adjustable parameters (length, contact transmission, temperature, \u2026). When the intrinsic backscattering at the contacts is weak (i.e., the conductance is close to 2e\u00b2/h at high temperature), we predict that this behavior should be described by a universal function. For short such wires, the charge increases roughly linearly with V_G, with small oscillations due to quantum interference between electrons scattered at the contacts. For longer wires at low temperature, Coulomb blockade behavior sets in, and the charge increases in steps. In both limits \u2202Q/\u2202V_G, which should characterize the linear-response conductance, exhibits periodic peaks in V_G. We show that due to Coulomb interactions the period in the former limit is twice that of the latter, and describe the evolution of the peaks through this crossover. The study can be generalized to multichannel LL's, and may explain qualitatively the recent observation by Liang et al. [Phys. Rev. Lett. 88, 126801 (2002)] of a four-electron periodicity for electron addition in single-walled carbon nanotubes.", "doi": "10.1103/physrevb.69.155332", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2004-04-15", "series_number": "15", "volume": "69", "issue": "15", "pages": "Art. No. 155332" }, { "id": "authors:rtj6z-wx430", "collection": "authors", "collection_id": "rtj6z-wx430", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200225-123359581", "type": "article", "title": "Resistance of multilayers with long length scale interfacial roughness", "author": [ { "family_name": "Alicea", "given_name": "Jason", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Hershfield", "given_name": "Selman", "clpid": "Hershfield-Selman" } ], "abstract": "The resistance of multilayers with interfacial roughness on a length scale large compared to the layer spacing is obtained using the Boltzmann equation. Both the current-perpendicular-to-plane (CPP) and current-in-plane (CIP) geometries are considered in the limits where the mean-free paths are short and long compared to the atomic spacing. In the short mean-free path limit, the resistance decreases in the CPP geometry and increases in the CIP geometry. In the long mean-free path limit, the resistance increases in both configurations due to enhanced surface scattering. The giant magnetoresistance can either be enhanced or reduced by roughness depending on the sample parameters. Estimates of the short and long mean-free path effects in Fe/Cr multilayers are obtained using experimentally determined parameters.", "doi": "10.1063/1.1555799", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "2003-05-15", "series_number": "10", "volume": "93", "issue": "10", "pages": "7930-7932" } ]