Research On Edge State Of Two-dimensional Acoustic Topology Materials And Their Applications

In recent years,the concept of topology in condensed matter physics has been introduced to the field of acoustics,and become one of the important branches in acoustics.Acoustic topological insulators,possessing the edge states within the band gaps,have enormous potential applications in sound wave transmission,acoustic device design,and sound wave control.Up to now,researchers have realized various analogues of quantum topological phases in the field of acoustics.These theoretical and experimental works provide new ideas and methods for the design of novel high-robustness acoustic functional devices,which are expected to have a far impact in the areas of acoustic devices,sound wave communication,and noise control.The thesis focuses on the design of acoustic functional devices based on acoustic topological insulators,aiming to provide new schemes for applications acoustic topological insulators.Apart from the introduction in Chapter 1 and the summary and outlook in Chapter 7,the content of this thesis contains five parts:(1)theoretical research and experimental measurement methods;(2)valley sound energy transport based on symmetric and antisymmetric valley edge modes in honeycomb sonic crystals;(3)tunable dual-functional acoustic logic gates based on valley topological transport;(4)programmable dual-band acoustic topological insulators;(5)corner states in acoustic high-order topological insulators with honeycomb lattice.The detailed descriptions for each part are list as following:In Chapter 2,the basic theories and experimental research methods are introduced,including sonic crystal band theory,the basic principles of the finite element method,experimental equipment and measurement methods for sound transmission rate,and the sonic crystal dispersion relation.In Chapter 3,two valley topological waveguides with different interfaces(I and II)are designed based on the honeycomb-type sonic crystal.Simulation results show that the valley edge states in interfaces I and II have antisymmetric and symmetric distribution characteristics,respectively.On the basis of this characteristics,a pair of out-phase and in-phase sound sources are used to excite the antisymmetric and symmetric valley edge states in the valley topological waveguides with interfaces I and II,realizing valley edge transport.In addition,Z-shaped and Vshaped defects are introduced to further demonstrate the robustness of the valley edge transport.Finally,a pair of sound sources are placed on both sides of the valley topological waveguides,and by actively controlling the initial phase of the sound sources,a tunable asymmetric acoustic transmission effect is designed and implemented.This research provides design ideas and theoretical schemes for the development of highly robust and controllable topological acoustic devices.In Chapter 4,a tunable dual-functional acoustic logic gate is designed based on honeycomb sonic crystals.Using a pair of sound sources to excite the valley topological insulator with either interface I or II,the dual-functional acoustic logic gate is realized.By actively adjusting the phase of the two sound sources,logic functions "OR" and "XOR" can be switched.Moreover,the robustness of the logic gate is experimentally verified by introducing a V-shaped defect in interface I or II.The designed acoustic logic gate has the advantages of simplicity,high robustness,and controllability.In Chapter 5,a one-dimensional programmable dual-band acoustic topological insulator is designed which is composed of digital units "1" and "0".Each unit consists of three cylindrical scatterers with different diameters.By periodically arranging the units "1" and "0",a onedimensional acoustic topological insulator is constructed,and topological interface states are observed in both band gaps.Furthermore,a one-dimensional dual-band acoustic topological insulator with programmable functionality is realized based on reconfigurable units and the corresponding automated control system.By programming different coding sequences on a PC,the position of the interface states can be controlled arbitrarily.This research provides a new approach for the development of intelligent and programmable multi-band acoustic devices.In Chapter 6,corner states in high-order acoustic topological insulators have been investigated.The high-order acoustic topological insulator is composed of a honeycomb lattice sonic crystal.By rotating the unit at the top corner of the high-order topological insulator interface,the degeneracy of the corner states can be broken.Based on it,an acoustic encrypted communication receiver is proposed.This research provides new ideas and solutions for the design of novel acoustic communication devices,which have great potential applications in the fields of integrated acoustics,sound communication,and information processing.