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Spin-polarized quasiparticle transport in cuprate superconductors

Fu, C.-C. and Huang, Z. and Yeh, N.-C. (2002) Spin-polarized quasiparticle transport in cuprate superconductors. Physical Review B, 65 (22). Art. No. 224516. ISSN 1098-0121.

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The effects of spin-polarized quasiparticle transport in superconducting YBa2Cu3O7-delta (YBCO) epitaxial films are investigated by means of current injection into perovskite ferromagnet-insulator-superconductor (F-I-S) heterostructures. These effects are compared with the injection of simple quasiparticles into control samples of perovskite nonmagnetic metal-insulator-superconductor (N-I-S). Systematic studies of the critical current density (J(c)) as a function of the injection current density (J(inj)), temperature (T), and the thickness (d) of the superconductor reveal drastic differences between the F-I-S and N-I-S heterostructures, with strong suppression of J(c) and a rapidly increasing characteristic transport length near the superconducting transition temperature T-c only in the F-I-S samples. The temperature dependence of the efficiency (etaequivalent toDeltaJ(c)/J(inj); DeltaJ(c): the suppression of critical current due to finite J(inj)) in the F-I-S samples is also in sharp contrast to that in the N-I-S samples, suggesting significant redistribution of quasiparticles in F-I-S due to the longer lifetime of spin-polarized quasiparticles. Application of conventional theory for nonequilibrium superconductivity to these data further reveal that a substantial chemical potential shift mu(*) in F-I-S samples must be invoked to account for the experimental observation, whereas no discernible chemical potential shift exists in the N-I-S samples, suggesting strong effects of spin-polarized quasiparticles on cuprate superconductivity. The characteristic times estimated from our studies are suggestive of anisotropic spin relaxation processes, possibly with spin-orbit interaction dominating the c-axis spin transport and exchange interaction prevailing within the CuO2 planes. Several alternative scenarios attempted to account for the suppression of critical currents in F-I-S samples are also critically examined, and are found to be neither compatible with experimental data nor with the established theory of nonequilibrium superconductivity.

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Yeh, N.-C.0000-0002-1826-419X
Additional Information:© 2002 The American Physical Society. Received 18 October 2001; revised 14 January 2002; published 10 June 2002. The work at Caltech was jointly supported by NSF Grant No. DMR-0103045 and NASA/OSS. We are grateful to Dr. R. P. Vasquez at the Jet Propulsion Laboratory for providing the F-I-S and N-I-S heterostructures, performing the XPS characterization, and for useful discussions.
Funding AgencyGrant Number
Subject Keywords:high-temperature superconductivity, d-wave superconductors, T-C, pairing symmetry, andreev reflection, nonequilibrium superconductivity, tunneling spectroscopy, potential difference, injection devices, epitaxial-films
Issue or Number:22
Classification Code:PACS numbers: 74.50.1r, 74.40.1k, 74.80.Dm, 74.60.Jg
Record Number:CaltechAUTHORS:FUCprb02
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:867
Deposited By: Tony Diaz
Deposited On:31 Oct 2005
Last Modified:02 Oct 2019 22:37

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