Monograph records
https://feeds.library.caltech.edu/people/Refael-G/monograph.rss
A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenWed, 07 Feb 2024 02:49:14 +0000A Mott Glass to Superfluid Transition for Random Bosons in Two Dimensions
https://resolver.caltech.edu/CaltechAUTHORS:20111031-090402654
Authors: {'items': [{'id': 'Iyer-S', 'name': {'family': 'Iyer', 'given': 'S.'}}, {'id': 'Pekker-D', 'name': {'family': 'Pekker', 'given': 'D.'}}, {'id': 'Refael-G', 'name': {'family': 'Refael', 'given': 'G.'}}]}
Year: 2011
DOI: 10.48550/arXiv.1110.3338
We study the zero temperature superfluid-insulator transition for a two-dimensional model of
interacting, lattice bosons in the presence of quenched disorder and particle-hole symmetry. We
follow the approach of a recent series of papers by Altman, Kafri, Polkovnikov, and Refael, in which
the strong disorder renormalization group is used to study disordered bosons in one dimension.
Adapting this method to two dimensions, we study several different species of disorder and uncover
universal features of the superfluid-insulator transition. In particular, we locate an unstable finite
disorder fixed point that governs the transition between the superfluid and a gapless, glassy insulator.
We present numerical evidence that this glassy phase is the incompressible Mott glass and that the
transition from this phase to the superfluid is driven by percolation-type process. Finally, we provide
estimates of the critical exponents governing this transition.https://authors.library.caltech.edu/records/r34va-8s370Enhancement of surface photocurrents in topological insulators using magnetic superlattices
https://resolver.caltech.edu/CaltechAUTHORS:20140715-162801579
Authors: {'items': [{'id': 'Lindner-N-H', 'name': {'family': 'Lindner', 'given': 'Netanel H.'}, 'orcid': '0000-0003-1879-3902'}, {'id': 'Refael-G', 'name': {'family': 'Refael', 'given': 'Gil'}}, {'id': 'von-Oppen-F', 'name': {'family': 'von Oppen', 'given': 'Felix'}}]}
Year: 2014
DOI: 10.48550/arXiv.1403.0010v1
The gapless surface states of topological insulators (TI) can potentially be used to detect and harvest low-frequency infrared light. Nonetheless, it was shown that significant surface photocurrents due to light with frequency below
the bulk gap are rather hard to produce. Here we demonstrate that a periodic
magnetic pattern added to the surface dramatically enhances surface photocurrents in TI's . The ability to produce substantial photocurrents on TI surfaces from mid-range and far-infrared light could be used in photovoltaic applications, as well as for detection of micrometer wavelength radiation.https://authors.library.caltech.edu/records/ht0vt-5qb26Variational-Correlations Approach to Quantum Many-body Problems
https://resolver.caltech.edu/CaltechAUTHORS:20200303-081122185
Authors: {'items': [{'id': 'Haim-Arbel', 'name': {'family': 'Haim', 'given': 'Arbel'}}, {'id': 'Kueng-R-J', 'name': {'family': 'Kueng', 'given': 'Richard'}}, {'id': 'Refael-G', 'name': {'family': 'Refael', 'given': 'Gil'}}]}
Year: 2020
DOI: 10.48550/arXiv.2001.06510
We investigate an approach for studying the ground state of a quantum many-body Hamiltonian that is based on treating the correlation functions as variational parameters. In this approach, the challenge set by the exponentially-large Hilbert space is circumvented by approximating the positivity of the density matrix, order-by-order, in a way that keeps track of a limited set of correlation functions. In particular, the density-matrix description is replaced by a correlation matrix whose dimension is kept linear in system size, to all orders of the approximation. Unlike the conventional variational principle which provides an upper bound on the ground-state energy, in this approach one obtains a lower bound instead. By treating several one-dimensional spin 1/2 Hamiltonians, we demonstrate the ability of this approach to produce long-range correlations, and a ground-state energy that converges to the exact result. Possible extensions, including to higher-excited states are discussed.https://authors.library.caltech.edu/records/kx3az-ex716Controlling ligand-mediated exchange interactions in periodically driven magnetic materials
https://resolver.caltech.edu/CaltechAUTHORS:20200928-150652942
Authors: {'items': [{'id': 'Chaudhary-Swati', 'name': {'family': 'Chaudhary', 'given': 'Swati'}}, {'id': 'Ron-Alon', 'name': {'family': 'Ron', 'given': 'Alon'}}, {'id': 'Hsieh-David', 'name': {'family': 'Hsieh', 'given': 'David'}, 'orcid': '0000-0002-0812-955X'}, {'id': 'Refael-G', 'name': {'family': 'Refael', 'given': 'Gil'}}]}
Year: 2020
DOI: 10.48550/arXiv.2009.00813
A periodic drive could alter the effective exchange interactions in magnetic materials. Here, we explore how exchange pathways affect the effective interactions of periodically driven magnetic materials. Aiming to apply Floquet engineering methods to two-dimensional magnetic materials, we consider realistic models and discuss the effect of a periodic drive on ligand-mediated exchange interactions. We show that depending on bond angles and the number of ligand ions involved in the exchange process, drive-induced changes can be very different from those calculated from direct-hopping models considered earlier. We study these effects and find that the presence of ligand ions must be taken into account, especially for TMTCs where ligand ion mediated next-neighbor interactions play a crucial role in determining the magnetic ground state of the system.https://authors.library.caltech.edu/records/zkfxy-f6k81Stirring by Staring: Measurement Induced Chirality
https://resolver.caltech.edu/CaltechAUTHORS:20220113-182208459
Authors: {'items': [{'id': 'Wampler-Matthew', 'name': {'family': 'Wampler', 'given': 'Matthew'}}, {'id': 'Khor-Brian-J-J', 'name': {'family': 'Khor', 'given': 'Brian J. J.'}}, {'id': 'Refael-G', 'name': {'family': 'Refael', 'given': 'Gil'}}, {'id': 'Klich-Israel', 'name': {'family': 'Klich', 'given': 'Israel'}, 'orcid': '0000-0002-8979-0170'}]}
Year: 2021
DOI: 10.48550/arXiv.2108.05906
Controlling the dynamics of quantum systems is a current frontier of quantum many-body physics. Recent advancements in experimental techniques suggest exciting new directions in drive-induced quantum states. Here, we present a simple scheme that relies solely on occupation measurements to induce a chiral quantum phase. Namely, we show that by utilizing a pattern of repeated quantum measurements we can produce chiral edge transport of fermions hopping on a Lieb lattice. We study in detail the dependence on measurement frequency, showing that in the Zeno limit the system can be described by a classical stochastic dynamics, yielding protected transport. As the frequency of measurements is reduced, the charge flow is reduced and vanishes when no measurements are done.https://authors.library.caltech.edu/records/0vv01-b1807Ascendance of Superconductivity in Magic-Angle Graphene Multilayers
https://resolver.caltech.edu/CaltechAUTHORS:20220113-234609742
Authors: {'items': [{'id': 'Zhang-Yiran', 'name': {'family': 'Zhang', 'given': 'Yiran'}, 'orcid': '0000-0002-8477-0074'}, {'id': 'Polski-Robert-M', 'name': {'family': 'Polski', 'given': 'Robert'}, 'orcid': '0000-0003-0887-8099'}, {'id': 'Lewandowski-Cyprian', 'name': {'family': 'Lewandowski', 'given': 'Cyprian'}, 'orcid': '0000-0002-6944-9805'}, {'id': 'Thomson-Alex', 'name': {'family': 'Thomson', 'given': 'Alex'}, 'orcid': '0000-0002-9938-5048'}, {'id': 'Peng-Yang', 'name': {'family': 'Peng', 'given': 'Yang'}, 'orcid': '0000-0002-8868-2928'}, {'id': 'Choi-Youngjoon', 'name': {'family': 'Choi', 'given': 'Youngjoon'}}, {'id': 'Kim-Hyunjin', 'name': {'family': 'Kim', 'given': 'Hyunjin'}, 'orcid': '0000-0001-9886-0487'}, {'id': 'Watanabe-Kenji', 'name': {'family': 'Watanabe', 'given': 'Kenji'}, 'orcid': '0000-0003-3701-8119'}, {'id': 'Taniguchi-Takashi', 'name': {'family': 'Taniguchi', 'given': 'Takashi'}, 'orcid': '0000-0002-1467-3105'}, {'id': 'Alicea-J', 'name': {'family': 'Alicea', 'given': 'Jason'}, 'orcid': '0000-0001-9979-3423'}, {'id': 'von-Oppen-Felix', 'name': {'family': 'von Oppen', 'given': 'Felix'}, 'orcid': '0000-0002-2537-7256'}, {'id': 'Refael-G', 'name': {'family': 'Refael', 'given': 'Gil'}}, {'id': 'Nadj-Perge-S', 'name': {'family': 'Nadj-Perge', 'given': 'Stevan'}, 'orcid': '0000-0002-2394-9070'}]}
Year: 2022
DOI: 10.48550/arXiv.2112.09270
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.https://authors.library.caltech.edu/records/n990w-e2f28Topological frequency conversion in Weyl semimetals
https://resolver.caltech.edu/CaltechAUTHORS:20220224-200907852
Authors: {'items': [{'id': 'Nathan-Frederik', 'name': {'family': 'Nathan', 'given': 'Frederik'}, 'orcid': '0000-0001-9700-0231'}, {'id': 'Martin-Ivar', 'name': {'family': 'Martin', 'given': 'Ivar'}, 'orcid': '0000-0002-2010-6449'}, {'id': 'Refael-G', 'name': {'family': 'Refael', 'given': 'Gil'}}]}
Year: 2022
DOI: 10.48550/arXiv.2201.07804
We show that a Weyl semimetal irradiated at two distinct frequencies can convert energy between the frequencies at a potentially large rate. The phenomenon is a realization of topological frequency conversion from [Martin et al, PRX 7 041008 (2017)]. When the effect is realized, each electron near a Weyl point acts as a topological frequency converter, and converts energy at a universal rate given by Planck's constant multiplied by the product of the two frequencies. Our results indicate that Weyl points in TaAs support topological frequency conversion in the THz regime at achievable intensities of order 100 W/mm2. When the topological energy conversion rate exceeds the dissipation rate, the effect can be used for optical amplification. This amplification regime can be achieved when the relaxation rate of the system is larger than the characteristic driving period. This phenomenon further amplifies Weyl semimetals' promise for optical amplification and terahertz (THz) generation.https://authors.library.caltech.edu/records/0pn1a-12057Universal transport in periodically driven systems without long-lived quasiparticles
https://resolver.caltech.edu/CaltechAUTHORS:20220329-173619034
Authors: {'items': [{'id': 'Esin-Iliya', 'name': {'family': 'Esin', 'given': 'Iliya'}, 'orcid': '0000-0003-2959-0617'}, {'id': 'Kuhlenkamp-Clemens', 'name': {'family': 'Kuhlenkamp', 'given': 'Clemens'}, 'orcid': '0000-0001-5529-4358'}, {'id': 'Refael-G', 'name': {'family': 'Refael', 'given': 'Gil'}}, {'id': 'Berg-Erez', 'name': {'family': 'Berg', 'given': 'Erez'}, 'orcid': '0000-0001-8956-3384'}, {'id': 'Rudner-Mark-S', 'name': {'family': 'Rudner', 'given': 'Mark S.'}, 'orcid': '0000-0002-5150-6234'}, {'id': 'Lindner-Netanel-H', 'name': {'family': 'Lindner', 'given': 'Netanel H.'}, 'orcid': '0000-0003-1879-3902'}]}
Year: 2022
DOI: 10.48550/arXiv.2203.01313
An intriguing regime of universal charge transport at high entropy density has been proposed for periodically driven interacting one-dimensional systems with Bloch bands separated by a large single-particle band gap. For weak interactions, a simple picture based on well-defined Floquet quasiparticles suggests that the system should host a quasisteady state current that depends only on the populations of the system's Floquet-Bloch bands and their associated quasienergy winding numbers. Here we show that such topological transport persists into the strongly interacting regime where the single-particle lifetime becomes shorter than the drive period. Analytically, we show that the value of the current is insensitive to interaction-induced band renormalizations and lifetime broadening when certain conditions are met by the system's non-equilibrium distribution function. We show that these conditions correspond to a quasisteady state. We support these predictions through numerical simulation of a system of strongly interacting fermions in a periodically-modulated chain of Sachdev-Ye-Kitaev dots. Our work establishes universal transport at high entropy density as a robust far from equilibrium topological phenomenon, which can be readily realized with cold atoms in optical lattices.https://authors.library.caltech.edu/records/3y6s2-zzm18Hierarchy of Symmetry Breaking Correlated Phases in Twisted Bilayer Graphene
https://resolver.caltech.edu/CaltechAUTHORS:20220524-180258498
Authors: {'items': [{'id': 'Polski-Robert-M', 'name': {'family': 'Polski', 'given': 'Robert'}, 'orcid': '0000-0003-0887-8099'}, {'id': 'Zhang-Yiran', 'name': {'family': 'Zhang', 'given': 'Yiran'}, 'orcid': '0000-0002-8477-0074'}, {'id': 'Peng-Yang', 'name': {'family': 'Peng', 'given': 'Yang'}, 'orcid': '0000-0002-8868-2928'}, {'id': 'Arora-Harpreet-Singh', 'name': {'family': 'Arora', 'given': 'Harpreet Singh'}, 'orcid': '0000-0002-7674-735X'}, {'id': 'Choi-Youngjoon', 'name': {'family': 'Choi', 'given': 'Youngjoon'}, 'orcid': '0000-0001-9783-5992'}, {'id': 'Kim-Hyunjin', 'name': {'family': 'Kim', 'given': 'Hyunjin'}, 'orcid': '0000-0001-9886-0487'}, {'id': 'Watanabe-Kenji', 'name': {'family': 'Watanabe', 'given': 'Kenji'}, 'orcid': '0000-0003-3701-8119'}, {'id': 'Taniguchi-Takashi', 'name': {'family': 'Taniguchi', 'given': 'Takashi'}, 'orcid': '0000-0002-1467-3105'}, {'id': 'Refael-G', 'name': {'family': 'Refael', 'given': 'Gil'}}, {'id': 'von-Oppen-Felix', 'name': {'family': 'von Oppen', 'given': 'Felix'}, 'orcid': '0000-0002-2537-7256'}, {'id': 'Nadj-Perge-S', 'name': {'family': 'Nadj-Perge', 'given': 'Stevan'}, 'orcid': '0000-0002-2394-9070'}]}
Year: 2022
DOI: 10.48550/arXiv.2205.05225
Twisted bilayer graphene (TBG) near the magic twist angle of ∼1.1° exhibits a rich phase diagram. However, the interplay between different phases and their dependence on twist angle is still elusive. Here, we explore the stability of various TBG phases and demonstrate that superconductivity near filling of two electrons per moiré unit cell alongside Fermi surface reconstructions, as well as entropy-driven high-temperature phase transitions and linear-in-T resistance occur over a range of twist angles which extends far beyond those exhibiting correlated insulating phases. In the vicinity of the magic angle, we also find a metallic phase that displays a hysteretic anomalous Hall effect and incipient Chern insulating behaviour. Such a metallic phase can be rationalized in terms of the interplay between interaction-driven deformations of TBG bands leading to Berry curvature redistribution and Fermi surface reconstruction. Our results provide an extensive perspective on the hierarchy of correlated phases in TBG as classified by their robustness against deviations from the magic angle or, equivalently, their electronic interaction requirements.https://authors.library.caltech.edu/records/06ybb-rx004Generating coherent phonon waves in narrow-band materials: a twisted bilayer graphene phaser
https://resolver.caltech.edu/CaltechAUTHORS:20220816-183030641
Authors: {'items': [{'id': 'Esin-Iliya', 'name': {'family': 'Esin', 'given': 'Iliya'}, 'orcid': '0000-0003-2959-0617'}, {'id': 'Esterlis-Ilya', 'name': {'family': 'Esterlis', 'given': 'Ilya'}, 'orcid': '0000-0003-4775-9105'}, {'id': 'Demler-Eugene-A', 'name': {'family': 'Demler', 'given': 'Eugene'}, 'orcid': '0000-0002-2499-632X'}, {'id': 'Refael-G', 'name': {'family': 'Refael', 'given': 'Gil'}}]}
Year: 2022
DOI: 10.48550/arXiv.2207.11245
Twisted bilayer graphene (TBG) exhibits extremely low Fermi velocities for electrons, with the speed of sound surpassing the Fermi velocity. This regime enables the use of TBG for amplifying vibrational waves of the lattice through stimulated emission, following the same principles of operation of free-electron lasers. Our work proposes a lasing mechanism relying on the slow-electron bands to produce a coherent beam of acoustic phonons. We propose a device based on undulated electrons in TBG, which we dub the phaser. The device generates phonon beams in a terahertz (THz) frequency range, which can then be used to produce THz electromagnetic radiation. The ability to generate coherent phonons in solids breaks new ground in controlling quantum memories, probing quantum states, realizing non-equilibrium phases of matter, and designing new types of THz optical devices.https://authors.library.caltech.edu/records/zkt65-24m51