一维颗粒声子晶体的拓扑相变及可调界面态  

The topological phase transition and the tunable interface states in granular crystal

作　　者：李锋 黄学勤 陆久阳 刘正猷[2] 

机构地区：[1]华南理工大学物理与光电学院,广州510640 [2]武汉大学物理科学与技术学院,武汉430072

出　　处：《物理学报》2017年第22期55-62,共8页Acta Physica Sinica

基　　金：国家重点基础研究发展计划(批准号:2015CB755500);国家自然科学基金(批准号:61271139;11572318;11604102;11374233);广东省引进创新创业团队项目(批准号:2016ZT06C594);博士后创新人才支持计划(批准号:BX201600054)资助的课题~~

摘　　要：基于Su-Schrieffer-Heeger模型,构造了一种一维非线性声子晶体,通过调控外加在声子晶体上的预紧力,可调控声子晶体的拓扑态,从而实现拓扑相变.利用这一效应,把该非线性声子晶体与另一线性声子晶体形成异质结构,可以实现一种新型声学开关:通过调节预紧力即调控非线性声子晶体的拓扑相,可以实现异质结构中界面态从无到有的转变,从而实现了开关效应.利用该效应可望开发新型声学器件,如可调谐振器、可调滤波器、可调隔振器等.Topological phase is a new degree of freedom to describe the state of matter in condensed matter physics. One could predict the existence of the interface state between two topological different phononic crystals. The band structures of phononic crystal depend on the characteristics of their composite and their combination, such as geometry, filling fraction,and stiffness. However, after the phononic crystal is fabricated out, it is relatively difficult to tune their band structure and its topology. In order to broaden the application scope of phononic crystals, different kinds of tunable phononic crystals have been proposed. One method to achieve this tunability is to introduce nonlinearity into the phononic crystals.Granular crystals is one type of tunable nonlinear material, whose nonlinearity stems from nonlinear Hertzian contact.By changing the static precompression, the dispersion of granular crystals can be tuned. In this paper, by combining topology with nonlinear we create a new type of interface state switch without changing the experimental setup. Based on the Su-Schrieffer-Heeger（SSH） model—an example of a one dimensional（1D） topological insulator, we present a 1D nonlinear granular crystal, to realize the topological transition by precompression. First, we construct a 1D mechanical structure, which is made up of nonlinear granular crystal and linear phononic crystal. The 1D nonlinear granular crystal is simplified as a ＂mass-spring＂ model with tunable elastic constant and invariable elastic constant. By calculating the band topology—the Zak phase, we found that the Zak phase of the two bands can switch from π to 0. There exist a critical precompression Fo, when F 〉F0 the Zak phase of the band is π, when F〈 Fo the Zak phase is 0. The granular crystal vary from nontrivial bandgap to trivial one as precompression gradually increase. This effect enables us to design interface state switch at the interface between granular crystals with trivial and nontrivial band gap. Furthermore,wh

关 键 词：界面态 可调 拓扑相变 颗粒声子晶体 

分 类 号：O735[理学—晶体学]