论文标题
S/F/Ti异质结构中的混合螺旋状态和超导二极管效应
Hybrid helical state and superconducting diode effect in S/F/TI heterostructures
论文作者
论文摘要
众所周知，在Zeeman场的存在下具有自旋轨道耦合（SOC）的均质超导系统的基态是所谓的螺旋状态，其特征是阶参数的相位调制，但超级电流密度为零。在这项工作中，我们通过考虑在3D拓扑绝缘子的顶部考虑S/F BiLayer，研究了具有空间分离超导性和交换场的混合系统中螺旋状态的实现。该系统的特征是强旋旋锁，因此为螺旋状态生成提供了最有利的条件。该分析基于微观绿色的功能基于微观理论。我们证明，在双层中，即使交换场具有非零的分量垂直于S/F界面，即使超导顺序参数和交换场在空间上分离，螺旋状态也可以生存。同时，在这种空间不均匀的情况下，螺旋状态伴随着分布在双层上的自发电流，其平均水平为零。此外，我们表明这种混合螺旋状态在系统中引起了非股展。我们证明了超导二极管效应的实现，并表明，由于自旋摩托锁定的最大可能值，因此在考虑的系统中的非次数程度非常大。
It is well-known that the ground state of homogeneous superconducting systems with spin-orbit coupling (SOC) in the presence of the Zeeman field is the so-called helical state, which is characterized by the phase modulation of the order parameter, but zero supercurrent density. In this work we investigate the realization of the helical state in a hybrid system with spatially separated superconductivity and exchange field by considering S/F bilayer on top of a 3D topological insulator. This system is characterized by strong spin-momentum locking and, consequently, provides the most favorable conditions for the helical state generation. The analysis is based on the microscopic theory in terms of the quasiclassical Green's functions. We demonstrate that in the bilayer the helical state survives if the exchange field has non-zero component perpendicular to the S/F interface even in spite of the fact that the superconducting order parameter and the exchange field are spatially separated. At the same time, in this spatially inhomogeneous situation the helical state is accompanied by the spontaneous currents distributed over the bilayer in such a way as to have zero average. Further, we show that this hybrid helical state gives rise to nonreciprocity in the system. We demonstrate the realization of the superconducting diode effect and show that the degree of nonreciprocity is very large in the considered system due to the strongest possible value of the spin-momentum locking.
