Abstract

Valley-Hall-like second-order photonic topological insulators in Kagome-lattice photonic crystals with C_3v point-group symmetry are elaborately analyzed. Different from conventional valley-Hall photonic topological insulators, the calculation results show the topological invariant of the Kagome insulators is more suitable to be described by quantized electric polarization rather than valley Chern numbers. Topological edge states are thoroughly investigated at almost all the possible zigzag-type and armchair-type interfaces between photonic crystals with different topological phases, presenting important features of valley-Hall phase such as robust transport with little backscattering. Zero-dimensional corner states in most available oblique corners with different angles formed by zigzag-type or armchair-type edges are also detailly studied, showing the second-order topological insulator signature. This work provides a guidance for the practical realization of topological waveguides and high-Q cavities with Kagome photonic crystals.

中文翻译：

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谷类霍尔光子Kagome绝缘体拓扑边缘和角态的详细分析

摘要

详细分析了具有C _3v点群对称性的Kagome 晶格光子晶体中的Valley-Hall 型二阶光子拓扑绝缘体。与传统的谷霍尔光子拓扑绝缘体不同，计算结果表明Kagome绝缘体的拓扑不变量更适合用量子化电极化而不是谷陈数来描述。在具有不同拓扑相的光子晶体之间几乎所有可能的锯齿型和扶手椅型界面上，对拓扑边缘态进行了彻底研究，呈现出谷-霍尔相的重要特征，例如具有很少反向散射的鲁棒传输。还详细研究了大多数可用的由锯齿型或扶手椅型边缘形成的不同角度的斜角中的零维角状态，显示了二阶拓扑绝缘体特征。这项工作为利用 Kagome 光子晶体实现拓扑波导和高 Q 腔提供了指导。