Suppression of Andreev conductance in a topological insulator-superconductor nanostep junction
Suppression of Andreev conductance in a topological insulator-superconductor nanostep junction
复制标题
拓扑绝缘体-超导体纳米台阶结中安德烈夫电导的抑制
DOI：
10.1088/1674-1056/25/3/037301
复制
发表时间：
2016
影响因子：
1.7
通讯作者：
Li Yu-Xian
中科院分区：
文献类型：
--
作者：
Zheng Yi-Jie;Song Jun-Tao;Li Yu-Xian
当两个三维拓扑绝缘体（TI）彼此靠近且表面对齐时，表面形成线结。类似地，不位于单个平面中的三个TI表面可以形成原子级纳米台阶结。本文从理论上研究了TI-TI-超导纳米台阶结中的Andreev反射。由于沿沿着每个线结的边缘态的存在，纳米台阶结的电导被抑制。当电子的入射能量大于超导带隙时，台阶结的Andreev电导小于1，而平面结的Andreev电导为1。Andreev电导被发现依赖于台阶结的高度。Andreev电导随结高的变化呈现出振荡行为，当λ = 0时，其振荡幅度保持不变，但当λ = Δ时，其振荡幅度减小，这与平面结的情况不同。因此，台阶的高度是纳米台阶结中Andreev反射的重要参数，并且起着与正常金属-超导体平面结中的δ势垒类似的作用。
When two three-dimensional topological insulators (TIs) are brought close to each other with their surfaces aligned, the surfaces form a line junction. Similarly, three TI surfaces, not lying in a single plane, can form an atomic-scale nanostep junction. In this paper, Andreev reflection in a TI–TI–superconductor nanostep junction is investigated theoretically. Because of the existence of edge states along each line junction, the conductance for a nanostep junction is suppressed. When the incident energy (ɛ) of an electron is larger than the superconductor gap (Δ), the Andreev conductance in a step junction is less than unity while for a plane junction it is unity. The Andreev conductance is found to depend on the height of the step junction. The Andreev conductance exhibits oscillatory behavior as a function of the junction height with the amplitude of the oscillations remaining unchanged when ɛ= 0, but decreasing for ɛ= Δ, which is different from the case of the plane junction. The height of the step is therefore an important parameter for Andreev reflection in nanostep junctions, and plays a role similar to that of the delta potential barrier in normal metal–superconductor plane junctions.