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Spin current in ferromagnet/insulator/superconductor junctions

S. Kashiwaya·Y. Tanaka·N. Yoshida·M. R. Beasley
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Abstract

A theory of spin polarized tunneling spectroscopy based on a scattering theory is given for tunneling junctions between ferromagnets and d-wave superconductors. The spin filtering effect of an exchange field in the insulator is also treated. We clarify that the properties of the Andreev reflection are largely modified due to a presence of an exchange field in the ferromagnets, and consequently the Andreev reflected quasiparticle shows an evanescent-wave behavior depending on the injection angle of the quasiparticle. Conductance formulas for the spin current as well as the charge current are given as a function of the applied voltage and the spin-polarization in the ferromagnet for arbitrary barrier heights. It is shown that the surface bound states do not contribute to the spin current and that the zero-bias conductance peak expected for a d-wave superconductor splits into two peaks under the influence of the exchange interaction in the insulator.

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S. Kashiwaya, Y. Tanaka, N. Yoshida, M. R. Beasley. 1999-04-04. Spin current in ferromagnet/insulator/superconductor junctions. https://doi.org/10.1103/physrevb.60.3572

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