Volpez Yanick, Loss Daniel, Klinovaja Jelena
Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
Phys Rev Lett. 2019 Mar 29;122(12):126402. doi: 10.1103/PhysRevLett.122.126402.
We consider a Josephson junction bilayer consisting of two tunnel-coupled two-dimensional electron gas layers with Rashba spin-orbit interaction, proximitized by a top and bottom s-wave superconductor with phase difference ϕ close to π. We show that, in the presence of a finite weak in-plane Zeeman field, the bilayer can be driven into a second order topological superconducting phase, hosting two Majorana corner states (MCSs). If ϕ=π, in a rectangular geometry, these zero-energy bound states are located at two opposite corners determined by the direction of the Zeeman field. If the phase difference ϕ deviates from π by a critical value, one of the two MCSs gets relocated to an adjacent corner. As the phase difference ϕ increases further, the system becomes trivially gapped. The obtained MCSs are robust against static and magnetic disorder. We propose two setups that could realize such a model: one is based on controlling ϕ by magnetic flux, the other involves an additional layer of randomly oriented magnetic impurities responsible for the phase shift of π in the proximity-induced superconducting pairing.
我们考虑一个约瑟夫森结双层结构，它由两个具有Rashba自旋轨道相互作用的二维电子气层通过隧道耦合而成，并由顶部和底部的s波超导体进行近邻效应诱导，且两者之间的相位差ϕ接近π。我们表明，在存在有限弱面内塞曼场的情况下，该双层结构可被驱动进入二阶拓扑超导相，其中存在两个马约拉纳角态（MCSs）。如果ϕ = π，在矩形几何结构中，这些零能量束缚态位于由塞曼场方向确定的两个对角处。如果相位差ϕ偏离π一个临界值，两个MCSs中的一个会重新定位到相邻的角上。随着相位差ϕ进一步增大，系统会变成平凡能隙态。所得到的MCSs对静态和磁无序具有鲁棒性。我们提出了两种可以实现这种模型的设置：一种是基于通过磁通量控制ϕ，另一种涉及额外一层随机取向的磁性杂质，其负责在近邻诱导超导配对中产生π的相移。
