Manifestation of triplet superconductivity in superconductor-ferromagnet structures
Manifestation of triplet superconductivity in superconductor-ferromagnet structures
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DOI：
10.1103/physrevb.68.064513
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发表时间：
2003-03
影响因子：
3.7
通讯作者：
F. Bergeret;A. F. Volkov;A. F. Volkov;K. B. Efetov;K. B. Efetov
中科院分区：
文献类型：
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作者：
F. Bergeret;A. F. Volkov;A. F. Volkov;K. B. Efetov;K. B. Efetov
本文研究了具有任意相对磁化方向M的多层超导/铁磁体（S/F）结构的邻近效应。如果不同层的磁化强度是共线的，那么在F层中诱导的超导凝聚函数只有一个单重态分量和一个三重态分量，库珀对的总磁矩在M方向上的投影为零。在这种情况下，凝聚体穿过F层的长度很短，由交换能J决定。如果磁化强度M不共线，则三重态分量除了零投影外，还有投影′ 1。后一个分量的动量是偶数，松原频率是奇数，穿透F层的距离很长，随着温度的降低而增加，并且不依赖于J（自旋轨道相互作用限制了这个长度）。如果F层的厚度远大于π J，则相邻S层之间的约瑟夫森耦合仅由三重态分量提供，从而在结构的横向方向上产生新型的超导性。对于矢量M的正（负）手征的情况，约瑟夫森临界电流为正（负）。我们证明，这种类型的三重态凝聚体也可以通过测量F/S/F结构的态密度来检测。
We study proximity effects in a multilayered superconductor/ferromagnet (S/F) structure with arbitrary relative directions of the magnetization M. If the magnetizations of different layers are collinear, the superconducting condensate function induced in the F layers has only a singlet component and a triplet one with a zero projection of the total magnetic moment of the Cooper pairs on the M direction. In this case the condensate penetrates the F layers over a short length ξ J determined by the exchange energy J. If the magnetizations M are not collinear, the triplet component has, in addition to the zero projection, the projections ′ 1. The latter component is even in the momentum, odd in the Matsubara frequency and penetrates the F layers over a long distance that increases with decreasing temperature and does not depend on J (the spin-orbit interaction limits this length). If the thickness of the F layers is much larger than ξ J , the Josephson coupling between neighboring S layers is provided only by the triplet component, so that a new type of superconductivity arises in the transverse direction of the structure. The Josephson critical current is positive (negative) for the case of a positive (negative) chirality of the vector M. We demonstrate that this type of the triplet condensate can be detected also by measuring the density of states in F/S/F structures.