The recently introduced classification of two-dimensional insulators in terms of topological crystalline invariants has been applied so far to "obstructed" atomic insulators characterized by a mismatch between the centers of the electronic Wannier functions and the ionic positions. We extend this notion to quantum spin Hall insulators in which the ground state cannot be described in terms of time-reversal symmetric localized Wannier functions. A system equivalent to graphene in all its relevant electronic and topological properties except for a real-space obstruction is identified and studied via symmetry analysis as well as with density functional theory. The low-energy model comprises a local spin-orbit coupling and a non-local symmetry breaking potential, which turn out to be the essential ingredients for an obstructed quantum spin Hall insulator. An experimental fingerprint of the obstruction is then measured in a large-gap triangular quantum spin Hall material.

中文翻译：

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量子自旋霍尔绝缘体中的实空间阻塞

最近引入的根据拓扑晶体不变量对二维绝缘体的分类迄今为止已应用于“受阻”原子绝缘体，其特征是电子 Wannier 函数的中心与离子位置之间的不匹配。我们将此概念扩展到量子自旋霍尔绝缘体，其中基态不能用时间反转对称局部 Wannier 函数来描述。通过对称性分析以及密度泛函理论，识别和研究了在所有相关电子和拓扑特性上与石墨烯等效的系统，除了真实空间的障碍物。低能模型包括局部自旋轨道耦合和非局部对称破缺势，事实证明，这是阻碍量子自旋霍尔绝缘体的基本成分。然后在大间隙三角量子自旋霍尔材料中测量障碍物的实验指纹。