Low-loss and broadband anomalous Floquet topological insulator for airborne sound

Abstract

Anomalous Floquet topological insulators (AFIs) for airborne sound have recently been realized in experiments. However, the implemented version suffers from significant loss and narrowband due to thermal viscosity and dispersive coupling strength between unit-cells. Here, we propose a solution for realizing low-loss and broadband acoustic AFI. We show that the loss after passing through one unit-cell can be less than 2% for the topological edge states. It is also theoretically unveiled that in the frequency range of nearly unitary coupling (∼0.97 from 4.8 kHz to 7.0 kHz in our case), around 84% corresponds to topological bands. Our proposal may promote the application of large-dimension acoustic topological devices.