Xu Yuanfeng, Song Zhida, Wang Zhijun, Weng Hongming, Dai Xi
Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Phys Rev Lett. 2019 Jun 28;122(25):256402. doi: 10.1103/PhysRevLett.122.256402.
Based on first-principles calculations and symmetry analysis, we propose that EuIn_{2}As_{2} is a long-awaited axion insulator with antiferromagnetic (AFM) long-range order. Characterized by the parity-based invariant Z_{4}=2, the topological magnetoelectric effect is quantized with θ=π in the bulk, with a band gap as large as 0.1 eV. When the staggered magnetic moments of the AFM phase are along the a or b axis, it is also a topological crystalline insulator phase with gapless surface states emerging on (100), (010), and (001) surfaces. When the magnetic moments are along the c axis, both the (100) and (001) surfaces are gapped, and the material can also be viewed as a high-order topological insulator with one-dimensional chiral states existing on the hinges between those gapped surfaces. We have calculated both the topological surface states and the hinge state in different phases of the system, respectively, which can be detected by angle-resolved photoemission spectroscopy or STM experiments.
基于第一性原理计算和对称性分析，我们提出EuIn₂As₂是一种期待已久的具有反铁磁（AFM）长程序的轴子绝缘体。其特征在于基于宇称的不变量Z₄ = 2，拓扑磁电效应在体相中以θ = π进行量子化，带隙高达0.1 eV。当AFM相的交错磁矩沿a或b轴时，它也是一种拓扑晶体绝缘体相，在（100）、（010）和（001）表面出现无隙表面态。当磁矩沿c轴时，（100）和（001）表面均有能隙，该材料也可被视为一种高阶拓扑绝缘体，在这些有能隙表面之间的棱边上存在一维手性态。我们分别计算了系统不同相中的拓扑表面态和棱边态，它们可通过角分辨光电子能谱或STM实验检测到。
