General boundary conditions for quasiclassical theory of superconductivity in the diffusive limit: application to strongly spin-polarized systems
General boundary conditions for quasiclassical theory of superconductivity in the diffusive limit: application to strongly spin-polarized systems
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DOI：
10.1088/1367-2630/17/8/083037
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发表时间：
2015-08-10
影响因子：
3.3
通讯作者：
Linder, J.
中科院分区：
文献类型：
--
作者：
Eschrig, M.;Cottet, A.;Linder, J.
准经典超导理论中的边界条件对于描述异质结构中的邻近效应是至关重要的。虽然他们已经推导出弹道的情况下，在充分的一般性，相应的边界条件的扩散限制，Usadel理论所描述的，一直缺乏界面涉及强自旋极化材料，例如半金属铁磁体。鉴于目前在超导自旋电子学的新兴领域的研究激烈，制定适当的边界条件Usadel理论的扩散超导体与强自旋极化铁磁体接触任意传输概率和任意自旋相关的界面散射相一直是一个燃烧的公开问题。在这里，我们关闭这个差距，并获得准经典绿色功能的扩散限制，有效的任何值的自旋极化，传输概率，自旋混合角（自旋相关的散射相移）的完整的边界条件。我们的配方也允许复杂的自旋纹理的接口和通道非对角散射（必要的成分时，接口两侧的通道数量不同）。作为一个例子，我们推导出表达式的邻近效应在扩散系统中涉及半金属铁磁体。在超导体/半金属/超导体约瑟夫森结中，我们发现在一定的界面条件下的phi（0）结行为。
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.