Spin injection into superconductors

Michael S. Osofsky; Robert J. Soulen Jr.; J. M. Byers; B. F. Woodfield; Douglas B. Chrisey; James S. Horwitz; Raymond C. Y. Auyeung

doi:10.1117/12.335914

22 December 1998 Spin injection into superconductors

Michael S. Osofsky, Robert J. Soulen Jr., J. M. Byers, B. F. Woodfield, Douglas B. Chrisey, James S. Horwitz, Raymond C. Y. Auyeung

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Proceedings Volume 3481, Superconducting and Related Oxides: Physics and Nanoengineering III; (1998) https://doi.org/10.1117/12.335914
Event: SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, 1998, San Diego, CA, United States

Abstract

The effect of spin-polarized injection on the superconductivity order parameter is investigated in a device consisting of YBa₂Cu₃O_7-(delta )/Au/Ni_0.8Fe_0.2 layers. A non-equilibrium theory which qualitatively agrees with the results of measurements made on superconductor/insulator/ferromagnet structures is presented. A quantitative analysis shows that this theory predicts injection currents that are several orders of magnitude too large. Recent results suggest that superconductivity in thin films can be strongly influenced by the injection of a spin- polarized current from a ferromagnetic material. The effect has been found to occur in both low T_c (Sn) and high T_c (YBa₂Cu₃O_7-(delta )) superconductors when either a conventional ferromagnetic metal, permalloy (Ni_0.8Fe_0.2), or a colossal magnetoresistive material were used as the source of spin polarization. Control experiments showed that unpolarized current from a nonmagnetic metal had comparatively little effect on the same superconductors. A phenomenological model, in which the energy gap of the superconductor is perturbed by the presence of excess spin polarized electrons, has been shown to qualitatively mimic the experimental results. However, an estimate of the current needed to significantly suppress the gap is shown to be several orders of magnitude larger than is observed.

Citation Download Citation

Michael S. Osofsky, Robert J. Soulen Jr., J. M. Byers, B. F. Woodfield, Douglas B. Chrisey, James S. Horwitz, and Raymond C. Y. Auyeung "Spin injection into superconductors", Proc. SPIE 3481, Superconducting and Related Oxides: Physics and Nanoengineering III, (22 December 1998); https://doi.org/10.1117/12.335914

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KEYWORDS

Superconductors

Quasiparticles

Phonons

Metals

Ferromagnetics

Superconductivity

Gold

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