[ { "id": "authors:n3aag-z4p34", "collection": "authors", "collection_id": "n3aag-z4p34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181213-143631375", "type": "book_section", "title": "Local and global effects of quantum impurities on the quasi-particle tunneling spectra of p-type and n-type cuprate superconductors", "book_title": "Superconducting and Related Oxides: Physics and Nanoengineering V", "author": [ { "family_name": "Yeh", "given_name": "N.-C.", "orcid": "0000-0002-1826-419X", "clpid": "Yeh-Nai-Chang" }, { "family_name": "Chen", "given_name": "C.-T.", "clpid": "Chen-Ching-Tzu" }, { "family_name": "Vasquez", "given_name": "R. P.", "clpid": "Vasquez-R-P" }, { "family_name": "Jung", "given_name": "C. U.", "clpid": "Jung-Chang-Uk" }, { "family_name": "Kim", "given_name": "J. Y.", "clpid": "Kim-Ju-Young" }, { "family_name": "Park", "given_name": "M. S.", "clpid": "Park-Min-Seok" }, { "family_name": "Kim", "given_name": "H. J.", "clpid": "Kim-Heon-Jung" }, { "family_name": "Lee", "given_name": "S. I.", "clpid": "Lee-Sung-Ik" }, { "family_name": "Yoshida", "given_name": "K.", "clpid": "Yoshida-Kentaroh" }, { "family_name": "Tajima", "given_name": "S.", "clpid": "Tajima-Setsuko" } ], "contributor": [ { "family_name": "Bozovic", "given_name": "Ivan", "clpid": "Bozovic-I" }, { "family_name": "Pavune", "given_name": "Davor", "clpid": "Pavuna-D" } ], "abstract": "We report scanning tunneling spectroscopic studies of the effects of quantum impurities on cuprate superconductors. The samples include p-type YBa_2Cu_3O_(7-\u03b4) single crystals with spinless impurities of Zn^(2+) and Mg^(2+) ((Zn,Mg)-YBCO) and n-type infinite-layer system Sr_(0.9)La)(0.1)CuO_2 with 1% magnetic Ni^(2+)- or 1% non-magnetic Zn^(2+)-impurities that substitute the Cu^(2+) in the CuO)2 plane. The local effects of spinless impurities on the quasiparticles spectra of (Zn,Mg)-YBCO are analogous to those of Zn-substituted Bi_2Sr_2CaCu_2O_(8+x), and the global effect is manifested by the suppression of the pairing potential \u0394d and of the spin excitation energy. In contrast, spectroscopic studies of Sr_(0.9)La_(0.1)CuO)2 reveal momentum-independent spectra and superconducting gap \u0394, with (2\u0394/k_BT_c) ~ 7 for T_c = 43 K and no pseudogap above T_c. The global response of Sr_(0.9)La_(0.1)CuO_2 to quantum impurities is similar to that of s-wave superconductors, being insensitive to small concentrations of spinless impurities (Zn) while showing rapid degradation in T_c with increasing magnetic impurities (Ni). Moreover, the spectra of the Ni-substituted Sr_(0.9)La_(0.1)CuO_2 reveal strong electron-hole asymmetry and long-range impurity effects, in contrast to the localized impurity effects in the p-type cuprates, and the introduction of Zn yield no reduction in either \u0394 or T_c. The physical implications of these findings are discussed.", "doi": "10.1117/12.452324", "isbn": "9780819445797", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "2002-11-07", "pages": "182-194" }, { "id": "authors:9qx8k-vv841", "collection": "authors", "collection_id": "9qx8k-vv841", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181204-132724823", "type": "book_section", "title": "Pairing symmetry and spin-polarized quasiparticle transport in high-temperature superconducting cuprates", "book_title": "Superconducting and Related Oxides: Physics and Nanoengineering IV", "author": [ { "family_name": "Yeh", "given_name": "N.-C.", "orcid": "0000-0002-1826-419X", "clpid": "Yeh-Nai-Chang" }, { "family_name": "Fu", "given_name": "C.-C.", "clpid": "Fu-Chu-Cheng" }, { "family_name": "Chen", "given_name": "C.-T.", "clpid": "Chen-Ching-Tzu" }, { "family_name": "Huang", "given_name": "Z.", "clpid": "Huang-Z" }, { "family_name": "Vasquez", "given_name": "R. P.", "clpid": "Vasquez-R-P" }, { "family_name": "Tajima", "given_name": "S.", "clpid": "Tajima-Setsuko" } ], "contributor": [ { "family_name": "Pavuna", "given_name": "Davor", "clpid": "Pavuna-D" }, { "family_name": "Bozovic", "given_name": "Ivan", "clpid": "Bozovic-I" } ], "abstract": "The pairing symmetry and the superconducting gap in high- temperature superconducting cuprates are investigated as a function of the hole doping level (x) and temperature (T), using directional scanning tunneling spectroscopy (STS). It is found that the predominant pairing symmetry is (d_(x^2 - y^2)), which is insensitive to the variations in T and x. In contrast, the maximum superconducting gap (\u0394_d) in YBa_2Cu_3O_(7-\u2202) and La_(2-x)Sr_xCuO_(4-\u2202) scales with the superconducting transition temperature (T_c), and the ratio of (2\u0394_d/k_BT)c) increases with decreasing doping level. The dominance of d_(x^2 - y^2) pairing is consistent with strong spatial variations in the local quasiparticle spectra near non-magnetic impurities such as Zn and Mg in a (Zn,Mg)-doped YBa_2Cu_3O_(7-\u2202) single crystal. To further elucidate the nature of the pairing state, the c-axis spin- polarized quasiparticle transport in the superconducting state of YBa_2Cu_3O_(7-\u2202) is investigated by studying the critical currents and STS under the injection of electrical currents from the underlying ferromagnetic La_(0.7)Sr_(0.3)MnO_3 layer in various ferromagnet-insulator-superconductor (F-I-S) heterostructures. The temperature dependent spin diffusion length (\u2202_s) and signatures of nonequilibrium quasiparticle distribution under spin injection in d-wave superconductors are determined for the first time.", "doi": "10.1117/12.397825", "isbn": "9780819436849", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "2000-09-06", "pages": "60-74" } ]