General boundary conditions for quasiclassical theory of superconductivity in the diffusive limit: application to strongly spin-polarized systems

被引:100
作者
Eschrig, M. [1 ,2 ]
Cottet, A. [3 ]
Belzig, W. [4 ]
Linder, J. [2 ]
机构
[1] Univ London, Dept Phys, Egham TW20 0EX, Surrey, England
[2] Norwegian Univ Sci & Technol, Dept Phys, N-7491 Trondheim, Norway
[3] Univ Paris Diderot, Sorbonne Paris Cite, Univ Paris 06,PSL Res Univ,CNRS, Sorbonne Univ,Lab Pierre Aigrain,Ecole Normale Su, F-75231 Paris 05, France
[4] Univ Konstanz, Dept Phys, D-78457 Constance, Germany
基金
英国工程与自然科学研究理事会;
关键词
superconducting spintronics; triplet supercurrents; boundary conditions; ACTIVE INTERFACES; UNCONVENTIONAL SUPERCONDUCTORS; QUASICLASSICAL EQUATIONS; ANDREEV SPECTROSCOPY; JOSEPHSON CURRENT; SUPERFLUID HE-3; GREEN-FUNCTION; FERROMAGNET; TRANSPORT; JUNCTION;
D O I
10.1088/1367-2630/17/8/083037
中图分类号
O4 [物理学];
学科分类号
0702 ;
摘要
Boundary conditions in quasiclassical theory of superconductivity are of crucial importance for describing proximity effects in heterostructures between different materials. Although they have been derived for the ballistic case in full generality, corresponding boundary conditions for the diffusive limit, described by Usadel theory, have been lacking for interfaces involving strongly spin-polarized materials, e.g. half-metallic ferromagnets. Given the current intense research in the emerging field of superconducting spintronics, the formulation of appropriate boundary conditions for the Usadel theory of diffusive superconductors in contact with strongly spin-polarized ferromagnets for arbitrary transmission probability and arbitrary spin-dependent interface scattering phases has been a burning open question. Here we close this gap and derive the full boundary conditions for quasiclassical Green functions in the diffusive limit, valid for any value of spin polarization, transmission probability, and spin-mixing angles (spin-dependent scattering phase shifts). Our formulation allows also for complex spin textures across the interface and for channel off-diagonal scattering (a necessary ingredient when the numbers of channels on the two sides of the interface differ). As an example we derive expressions for the proximity effect in diffusive systems involving half-metallic ferromagnets. In a superconductor/half-metal/superconductor Josephson junction we find phi(0)-junction behavior under certain interface conditions.
引用
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页数:21
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