Bai Chunxu, Yang Yanling
College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang, 464000, People's Republic of China.
J Phys Condens Matter. 2020 Aug 21;32(46). doi: 10.1088/1361-648X/abace4.
Nontrivial Rashba metal states in conventional semiconductor materials generated by both Rashba spin-orbit coupling and ferromagnetic exchange coupling coexisting were recently predicted and exploited. Single layered transition metal dichalcogenides (TMDC) featuring those states and their potential applications have been less focused. We find that, in the materials with Rashba spin-orbit coupling only, nontrivial Rashba metallic states can be manipulated by an external gate voltage. Based on extensive numerical simulations, the relationships between the supercurrent and nontrivial Rashba metallic states in the TMDC Josephson junction have been investigated. It is shown that, in the absence of the Rashba spin-orbit coupling, the critical supercurrent exhibits a stark difference between normal Rashba metal state and anomalous Rashba metal state in the finite junction as compared to the case of the short junction. While in the case of the finite Rashba spin-orbit coupling, the critical supercurrent demonstrates a reentrant behavior when Fermi level sweeps from anomalous Rashba metal state to Rashba ring metal state. Intriguingly, not only at the conversion of the nontrivial Rashba metallic states but also in the Rashba ring metal state the reentrant behavior exhibits again, which could be well explained by the mixing of spin-triplet Cooper pairs with spin-singlet Cooper pairs in Ising superconductor. Such a reentrant effect offers a new way to detect Ising superconductivity based on the TMDC systems. Meanwhile our study also clarified that the nontrivial Rashba metallic state plays an important role in controlling the supercurrent in the TMDC Josephson junction, which is useful for designing future superconducting devices.
最近预测并利用了由共存的Rashba自旋轨道耦合和铁磁交换耦合在传统半导体材料中产生的非平凡Rashba金属态。具有这些态的单层过渡金属二卤化物（TMDC）及其潜在应用较少受到关注。我们发现，在仅具有Rashba自旋轨道耦合的材料中，非平凡Rashba金属态可通过外部栅极电压进行调控。基于广泛的数值模拟，研究了TMDC约瑟夫森结中超电流与非平凡Rashba金属态之间的关系。结果表明，在没有Rashba自旋轨道耦合的情况下，与短结情况相比，有限结中的临界超电流在正常Rashba金属态和反常Rashba金属态之间表现出明显差异。而在有限Rashba自旋轨道耦合的情况下，当费米能级从反常Rashba金属态扫向Rashba环金属态时，临界超电流呈现出折返行为。有趣的是，不仅在非平凡Rashba金属态的转变处，而且在Rashba环金属态中也再次出现折返行为，这可以通过伊辛超导体中自旋三重态库珀对与自旋单重态库珀对的混合得到很好的解释。这种折返效应为基于TMDC系统检测伊辛超导性提供了一种新方法。同时我们的研究还阐明了非平凡Rashba金属态在控制TMDC约瑟夫森结中的超电流方面起着重要作用，这对于设计未来的超导器件很有用。
