Mao Ning, Li Runhan, Dai Ying, Huang Baibiao, Yan Binghai, Niu Chengwang
School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100, China.
Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel.
Adv Sci (Weinh). 2022 Sep;9(27):e2202564. doi: 10.1002/advs.202202564. Epub 2022 Jul 29.
Boundary obstructed topological phases caused by Wannier orbital shift between ordinary atomic sites are proposed, which, however, cannot be indicated by symmetry eigenvalues at high symmetry momenta (symmetry indicators) in bulk. On the open boundary, Wannier charge centers can shift to different atoms from those in bulk, leading to in-gap surface states, higher-order hinge states or corner states. To demonstrate such orbital shift-induced boundary obstructed topological insulators, eight material candidates are predicted, all of which are overlooked in the present topological databases. Metallic surface states, hinge states, or corner states cover the large bulk energy gap (e.g., more than 1 eV in TlGaTe ) at related boundary, which are ready for experimental detection. Additionally, these materials are also fragile topological insulators with hourglass-like surface states.
提出了由普通原子位点之间的万尼尔轨道位移引起的边界受阻拓扑相，然而，在体材料中高对称动量处的对称本征值（对称指标）无法表明这种拓扑相。在开放边界上，万尼尔电荷中心可以从体材料中的原子转移到不同的原子上，从而导致带隙表面态、高阶棱态或角态。为了证明这种由轨道位移引起的边界受阻拓扑绝缘体，预测了八种候选材料，目前的拓扑数据库中均未考虑这些材料。金属表面态、棱态或角态覆盖了相关边界处的大的体能隙（例如，在TlGaTe中超过1 eV），易于实验检测。此外，这些材料也是具有沙漏状表面态的易碎拓扑绝缘体。
