论文标题
准一维高阶拓扑绝缘子
Quasi-One-Dimensional Higher-Order Topological Insulators
论文作者
论文摘要
准1D材料BI $ _ {4} $ x $ _ {4} $（x = br，i）是$β$ phose中的原型弱拓扑绝缘子（Ti）。对于$α$阶段，最近的高通量数据库筛选表明，BI $ _ {4} $ br $ _ {4} $是一种罕见的高阶Ti（hoti），而Bi $ _ {4} $ _ {4} $ i $ _ {4} $具有琐碎的对称指标。在这里，我们表明，实际上，两个$α$阶段都是原始的hotis，但通过执行第一原理计算，分析耦合 - 边缘二聚体，检查表面晶格结构，构建紧密结合模型以及建立边界拓扑结构，具有独特的终止依赖性铰链状态模式。我们透露，反转中心的位置决定BI $ _ {4} $ br $ _ {4} $（bi $ _ {4} $ i $ _ {4} $）以相反的（相同的）表面或固有的（相同的）二聚式（相同的）二聚体（块或外部或外部）来源。我们提出了各种实验来检查我们的预测。鉴于沿原子链的上级铰链，室温下的结构过渡以及三个轴的极端各向异性，我们的结果不仅意味着除了对称性指标范围之外，还可能存在许多拓扑材料，而且还建立了新的TI范式和一个独特的材料平台，以探索微分，对称性，对称性，对称性，对称性，局限性，互动和互动。
Quasi-1D materials Bi$_{4}$X$_{4}$ (X=Br,I) are prototype weak topological insulators (TI) in the $β$ phase. For the $α$ phases, recent high-throughput database screening suggests that Bi$_{4}$Br$_{4}$ is a rare higher-order TI (HOTI) whereas Bi$_{4}$I$_{4}$ has trivial symmetry indicators. Here we show that in fact the two $α$ phases are both pristine HOTIs yet with distinct termination-dependent hinge state patterns by performing first-principles calculations, analyzing coupled-edge dimerizations, inspecting surface lattice structures, constructing tight-binding models, and establishing boundary topological invariants. We reveal that the location of inversion center dictates Bi$_{4}$Br$_{4}$ (Bi$_{4}$I$_{4}$) to feature opposite (the same) dimerizations of a surface or intrinsic (bulk or extrinsic) origin at two side cleavage surfaces. We propose a variety of experiments to examine our predictions. Given the superior hinges along atomic chains, the structural transition at room temperature, and the extreme anisotropies in three axes, our results not only imply the possible existence of many topological materials beyond the scope of symmetry indicators but also establish a new TI paradigm and a unique material platform for exploring the interplay of geometry, symmetry, topology, and interaction.
