论文标题
二维光子平方晶格的拓扑特性，没有$ C_4 $和$ M_ {x（y）} $ symmetries
Topological properties of two-dimensional photonic square lattice without $C_4$ and $M_{x(y)}$ symmetries
论文作者
论文摘要
丰富的拓扑现象，边缘状态和两种拐角状态在没有$ C_4 $和$ M_ {x（y）} $ symmetries的二维方形介电光子晶体中揭幕。具体而言，由于退化为$ c_4 $和$ m_ {x（y）} $的系统中不存在的非平凡的I型角状态，因此受到非零四极矩的保护，不再量化至$ 0.5 $。优秀的特性，例如提出了亚波长的定位和空气浓缩的场分布。由长期相互作用引起的II型角状态由于不对称而更容易实现。这项工作扩大了对称性破裂系统的拓扑物理学，并提供了潜在的应用。
Rich topological phenomena, edge states and two types of corner states, are unveiled in a two-dimensional square-lattice dielectric photonic crystal without both $C_4$ and $M_{x(y)}$ symmetries. Specifically, non-trivial type-I corner states, which do not exist in systems with $C_4$ and $M_{x(y)}$ since the degeneracy, are protected by non-zero quadrupole moment, no longer quantized to but less than $0.5$. Excellent properties, e.g. sub-wavelength localization and air-concentrated field distribution, are presented. Type-II corner states, induced by long-range interactions, are easier realized due to asymmetry. This work broadens the topological physics for the symmetries-broken systems and provides potential applications.
