Charge transport through spin-polarized tunnel junction between two spin-split superconductors
Charge transport through spin-polarized tunnel junction between two spin-split superconductors
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DOI：
10.1103/physrevb.100.184501
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发表时间：
2019-11-04
影响因子：
3.7
通讯作者：
Sebastian Bergeret, F.
中科院分区：
文献类型：
--
作者：
Rouco, Mikel;Chakraborty, Subrata;Sebastian Bergeret, F.
我们研究了由自旋极化隧道势垒连接的两个自旋分裂超导体之间的结的输运性质。超导体(S)中的自旋劈裂场是由相邻的任意磁化强度的铁磁绝缘层引起的。这项研究的目的有两个。一方面，我们提出了一个基于准经典格林函数的理论框架，用来根据描述约瑟夫森电流和准粒子电流的不同参数来计算它。当两个超导体的自旋分裂场非共线时，我们的理论预言了隧道微分电导Di/dV的定性新结果。我们还讨论了如何利用基于FI/S的结来实现电流-相关系中几何相移恒定的反常约瑟夫森结。因此，在S电极之间没有相位差的情况下，它们可能会表现出自发的三重态超电流。另一方面，我们给出了EUS/Al/AlOx/EUS/Al结的平面隧道谱结果，并用我们的理论模型再现了得到的Di/dV曲线。通过理论和实验的比较，揭示了结的本征参数，如超导序参数的大小、自旋分裂场和自旋弛豫的信息，以及两种EUS膜的性质，如它们的形貌、磁畴结构和磁各向异性。
We investigate transport properties of junctions between two spin-split superconductors linked by a spin-polarized tunneling barrier. The spin-splitting fields in the superconductors (S) are induced by adjacent ferromagnetic insulating (FI) layers with arbitrary magnetization. The aim of this study is twofold. On the one hand, we present a theoretical framework based on the quasiclassical Green's functions to calculate the Josephson and quasiparticle current through the junctions in terms of the different parameters characterizing it. Our theory predicts qualitative new results for the tunneling differential conductance, dI/dV, when the spin-splitting fields of the two superconductors are noncollinear. We also discuss how junctions based on FI/S can be used to realize anomalous Josephson junctions with a constant geometric phase shift in the current-phase relation. As a result, they may exhibit spontaneous triplet supercurrents in the absence of a phase difference between the S electrodes. On the other hand, we show results of planar tunneling spectroscopy of a EuS/Al/AlOx/EuS/Al junction and use our theoretical model to reproduce the obtained dI/dV curves. Comparison between theory and experiment reveals information about the intrinsic parameters of the junction, such as the size of the superconducting order parameter, spin-splitting fields and spin relaxation, and also about properties of the two EuS films, such as their morphology, domain structure, and magnetic anisotropy.