双表面周期性弹性声子晶体板中的谷拓扑态  

Valley topological states in double-surface periodic elastic phonon crystal plates

作　　者：李荫铭 孔鹏 毕仁贵 何兆剑 邓科 Li Yin-Ming;Kong Peng;Bi Ren-Gui;He Zhao-Jian;Deng Ke(Department of Physics,Jishou University,Jishou 416000,China)

机构地区：[1]吉首大学物理系,吉首416000

出　　处：《物理学报》2022年第24期248-254,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11964011,11764016);湖南省教育厅科研基金(批准号:20C1530);吉首大学基金(批准号:Jdy20027)资助的课题。

摘　　要：随着拓扑理论的概念被引入到人工结构的研究中,由于其具有传输保护、能量无损耗、缺陷免疫等新奇的物理性质,引起了广泛的关注.本文基于弹性材料设计了一种双表面周期性结构声子晶体,其上、下表面由周期性排列的三角棱柱散射体组成,在只关注面外模式的Lamb波的情况下,构建了弹性声子晶体的谷拓扑态.只需简单旋转散射体,体系就会出现能带的反转,研究发现通过调节散射体的高度,可以实现谷拓扑边缘态频率的调控,由不同的谷霍尔材料组成的边缘界面处可以实现较宽频率的激发,进一步证实了边缘态频率可调控的思想可以在弹性材料中实现,并利用两种不同相组成的声子晶体板研究了拓扑输运情况,表现出优异的输运性能.这为谷拓扑保护弹性波激发中实现新的自由度.The topological insulator,as its novel physical properties,such as transmission protection,energy loss free and defect immunity,has aroused much interest recently.It is necessary to introduce the concept of topology into elastic materials to enrich the research contents of elastic waves.The concept of valley state provides a simplest solution to realize topological states.In this work,we design a double surface periodic phononic crystal based on elastic material,the upper and lower surfaces are composed of periodically arranged triangular prismatic scatterers.Valley topological states of elastic phononic crystals are observed only when focusing on Lamb waves in out-of-plane mode by numerical simulation.We also analyze theoretically the valley Chern number.As the angle between the triangular prism and the positive direction of the X axis is greater than 0,the Chern number of K is 1/2;when the angle is less than 0,the Chern number is–1/2.The K has the number opposite to the Chern number.By simply tuning the geometry of the scatterer,the inversion of the energy band will occur and the topological phase transition will be realized.We find that the frequency of edge state in valley topology can be regulated by adjusting the heights of scatterers.Moreover,wide frequency excitation is achieved at the edge interface composed of different valley Hall materials,which proves that the idea of adjustable edge state frequency can be implemented in elastic materials.According to the two different valley phase phononic crystals,we study the topological transport,exhibiting excellent transmission performance,even the Z-shaped interface.We find that the designed double surface structure has a stronger immune effect to defects than single surface,achieving a new degree of freedom in the valley topology protection of elastic wave excitation.

关 键 词：弹性波 声子晶体 边缘态 拓扑输运 

分 类 号：O735[理学—晶体学]