Schrade Constantin, Zyuzin A A, Klinovaja Jelena, Loss Daniel
Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
Phys Rev Lett. 2015 Dec 4;115(23):237001. doi: 10.1103/PhysRevLett.115.237001. Epub 2015 Dec 1.
We study two microscopic models of topological insulators in contact with an s-wave superconductor. In the first model the superconductor and the topological insulator are tunnel coupled via a layer of randomly distributed scalar and of randomly oriented spin impurities. Here, we demonstrate that spin-flip tunneling dominates over the spin-conserving one. In the second model the tunnel coupling is realized by a spatially nonuniform array of single-level quantum dots with randomly oriented spins. We find that the tunnel region forms a π junction where the effective order parameter changes sign. Because of the random spin orientation, effectively both models exhibit time-reversal symmetry. The proposed π junctions support topological superconductivity without magnetic fields and can be used to generate and manipulate Kramers pairs of Majorana fermions by gates.
我们研究了与s波超导体接触的拓扑绝缘体的两个微观模型。在第一个模型中，超导体和拓扑绝缘体通过一层随机分布的标量和随机取向的自旋杂质层进行隧道耦合。在这里，我们证明了自旋翻转隧道效应比自旋守恒隧道效应占主导。在第二个模型中，隧道耦合由具有随机取向自旋的单能级量子点的空间非均匀阵列实现。我们发现隧道区域形成了一个π结，其中有效序参量发生符号变化。由于自旋取向随机，实际上这两个模型都表现出时间反演对称性。所提出的π结支持无磁场的拓扑超导性，并且可用于通过门来产生和操纵马约拉纳费米子的克莱默斯对。
