Acoustic realization of quadrupole topological insulators

TL;DR

This paper presents the first practical acoustic quadrupole topological insulator, overcoming previous implementation challenges by designing feasible acoustic hopping, and confirms its topological properties through experimental detection of responses at various sample regions.

Contribution

Introduces a feasible method to realize acoustic quadrupole topological insulators that emulate tight-binding models without negative hopping coefficients.

Findings

Experimental confirmation of quadrupole topology via acoustic responses

First acoustic realization of quadrupole topological insulator

Potential for robust acoustic sensing and energy trapping applications

Abstract

A quadrupole topological insulator, being one higher-order topological insulator with nontrivial quadrupole quantization, has been intensely investigated very recently. However, the tight-binding model proposed for such emergent topological insulators demands both positive and negative hopping coefficients, which imposes an obstacle in practical realizations. Here we introduce a feasible approach to design the sign of hopping in acoustics, and construct the first acoustic quadrupole topological insulator that stringently emulates the tight-binding model. The inherent hierarchy quadrupole topology has been experimentally confirmed by detecting the acoustic responses at the bulk, edge and corner of the sample. Potential applications can be anticipated for the topologically robust in-gap states, such as acoustic sensing and energy trapping.