基于结构反转二维光子晶体的拓扑相变及拓扑边界态的构建  

Topological phase transition based on structure reversal of two-dimensional photonic crystals and construction of topological edge states

作　　者：方云团[1] 王张鑫 范尔盼 李小雪 王洪金[1] Fang Yun-Tuan;Wang Zhang-Xin;Fan Er-Pan;Li Xiao-Xue;Wang Hong-Jin(School of Computer Science and Telecommunication Engineering,Jiangsu University,Zhenjiang 212013,China)

机构地区：[1]江苏大学计算机科学与通信工程学院,镇江212013

出　　处：《物理学报》2020年第18期24-32,共9页Acta Physica Sinica

基　　金：江苏省工业网络安全技术重点实验室开放基金(批准号:STICB201906)资助的课题.

摘　　要：构建了二维六角蜂窝晶格的两种结构,让散射体和基体材料反转.由于特有的点群对称,该晶格在布里渊区中心具有类比电子体系的p轨道和d轨道.在散射体和基体反转的两种结构中, p轨道和d轨道也直接实现了反转.定量分析了产生轨道反转的原因来自于低频局域共振产生空气带和介质带的反转.通过p轨道和d轨道的宇称特性,构建了类比电子体系量子自旋霍尔效应的赝自旋态.通过Γ点处有效哈密顿量的分析,揭示轨道反转导致的拓扑相变.通过结构的优化,构建了基于赝自旋的拓扑边界态.电磁波仿真模拟和能流矢量分析证明了结构具有电子体系量子自旋霍尔效应的特性,即自旋与传播方向锁定和拓扑保护.结果也证明经典波量子自旋霍尔效应的实现可以不经历带隙关闭的过程.与同类型的研究相比较,本文的结构不需要晶格的缩放,具有设计简单、带隙宽和边界态局域性较强的特点.Two kinds of two-dimensional photonic crystal with hexagonal honeycomb lattices are constructed in which the scatterer and the matrix materials are reversed. Due to the symmetry of special point group, the lattices have p and d orbitals in the center of Brillouin region, which are similar to those in the electronic system. With the structure reversal, the p and d orbitals are also directly inverted. Quantitative analysis shows that the orbital inversion is due to the inversion of air band and medium band because of the local resonance effect in the low frequency bands. Based on the parity properties of p and d orbitals, the pseudo spin states are constructed by analogy to the quantum spin Hall effect in electronic systems. The analysis of the effective Hamiltonian at Γ point shows that the topological phase transition caused by orbital inversion is revealed. The pseudo spin edge states construct an optimal structure. The electromagnetic wave simulations and energy flow vector analysis show that the structure edge takes on the properties of quantum spin Hall effect, namely, the propagation direction is locked by the spin direction and the propagation is topologically protected. The results also show that the quantum spin Hall effect can be realized without undergoing the closing of gap. The comparison among similar researches indicates that the realization of the pseudo spin states does not need the deformation of lattice, and the structure proposed in this work possesses the characteristics of simple design,wide band gap and strong edge localization.

关 键 词：光子晶体 结构反转 能带反转 拓扑相变 赝自旋 

分 类 号：O469[理学—凝聚态物理] O734[理学—电子物理学]