Universal Approach to Magnetic Second-Order Topological Insulator.,Physical Review Letters

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Universal Approach to Magnetic Second-Order Topological Insulator.
Physical Review Letters ( IF 8.1 ) Pub Date : 2020-07-30 , DOI: 10.1103/physrevlett.125.056402
Cong Chen _{1,

2} , Zhida Song ₃ , Jian-Zhou Zhao _{2,

4} , Ziyu Chen ₁ , Zhi-Ming Yu _{2,

5} , Xian-Lei Sheng _{1,

2} , Shengyuan A Yang _{2,

6}

Affiliation

We propose a universal practical approach to realize magnetic second-order topological insulator (SOTI) materials, based on properly breaking the time reversal symmetry in conventional (first-order) topological insulators. The approach works for both three dimensions (3D) and two dimensions (2D), and is particularly suitable for 2D, where it can be achieved by coupling a quantum spin Hall insulator with a magnetic substrate. Using first-principles calculations, we predict bismuthene on EuO(111) surface as the first realistic system for a two-dimensional magnetic SOTI. We explicitly demonstrate the existence of the protected corner states. Benefitting from the large spin-orbit coupling and sizable magnetic proximity effect, these corner states are located in a boundary gap

\sim 83 meV

, and hence can be readily probed in experiment. By controlling the magnetic phase transition, a topological phase transition between a first-order TI and a SOTI can be simultaneously achieved in the system. The effect of symmetry breaking, the connection with filling anomaly, and the experimental detection are discussed.

中文翻译：

电磁二阶拓扑绝缘子的通用方法。

基于适当打破常规（一阶）拓扑绝缘体中的时间反转对称性，我们提出一种通用的实用方法来实现磁性二阶拓扑绝缘体（SOTI）材料。该方法适用于三维（3D）和二维（2D），并且特别适用于2D，其中可以通过将量子自旋霍尔绝缘体与磁性基板耦合来实现。使用第一性原理计算，我们预测EuO（111）表面上的铋是二维磁性SOTI的第一个现实系统。我们明确证明了受保护的拐角状态的存在。得益于大的自旋轨道耦合和可观的磁邻近效应，这些角状态位于边界间隙中