基于蜂窝晶格声子晶体的双频带声拓扑绝缘体

Dual-band acoustic topological insulator based on honeycomb lattice sonic crystal

基于齿轮形散射体的蜂窝晶格声子晶体,研究设计赝自旋相关的双频带声拓扑绝缘体.选取不同的散射体结构参数,可以获得蜂窝晶格声子晶体的四重偶然简并狄拉克点与声拓扑相变.利用两种不同拓扑相的蜂窝晶格声子晶体设计实现声拓扑波导结构,并实验验证了赝自旋相关的边缘模式鲁棒性.此外,保持蜂窝晶格声子晶体的结构不变,同时可以在高频区域获得四重偶然简并狄拉克点与声拓扑相变.所设计的双频带声拓扑绝缘体在多频带声通讯与声信息处理方面具有潜在的应用前景.

Based on honeycomb-lattice sonic crystals with gear-like scatterers,we study and design a pseudospindependent dual-band acoustic topological insulator.Compared with cylindrical scatterers with only a single tunable structure parameter(radius),there exist four tunable parameters for the gear scatterer,which enables the sonic crystal to realize four-fold accidental degeneracy at two different frequencies simultaneously.By changing structure parameters of the gear-like scatterers,we can obtain topological phase transitions between two sonic crystals.Based on this,we design acoustic topological waveguides based on two honeycomb-lattice sonic crystals with different topological phases,and introduce two kinds of defects(a lattice disorder and a bend)into the topological waveguide near the domain wall.Numerical simulations show that pseudospin edge states almost immune to two types of defects and can pass through the topological waveguides with negligible backscatterings.Compared with the results for the topological waveguide without defects,the measured transmission spectra are almost unchanged with the two types of defects,which further experimentally verify the robustness of pseudospin-dependent edge states.Additionally,by keeping the structure of the sonic crystals unchanged,we can also obtain another four-fold accidental degenerate Dirac point and the corresponding topological sound phase transitions in the high-frequency region.The simulations show that there also exists a pair of edge states in the overlapped bulk bandgap of the two sonic crystals in the high-frequency region.It is worth noting that the tiny gap between two edge states is larger than that in the low-frequency region,which may arise from the greater difference between the distributions of pressure eigenfunction of two sonic crystals.The proposed dual-band acoustic topology insulator has potential applications in multi-band sound communication and sound information processing.