Acoustic Higher-Order Topological Insulators Protected by Multipole Chiral Numbers

TL;DR

This paper reports the first experimental realization of acoustic higher-order topological insulators protected by multipole chiral numbers, demonstrating multiple corner states and opening new avenues for sound control applications.

Contribution

It introduces the experimental demonstration of higher-order topological insulators in acoustics based on multipole chiral numbers, a novel topological invariant.

Findings

Observation of multiple corner states in acoustic crystals

Confirmation of topological protection by multipole chiral numbers

Potential for advanced sound manipulation and energy trapping

Abstract

Recently, the higher-order topological phases from the chiral AIII symmetry classes are characterized by a Z topological invariant known as the multipole chiral numbers, which indicate the number of degenerate zero-energy corner states at each corner. Here, we report the first experimental realization of higher-order topological insulators protected by multipole chiral numbers with using acoustic crystals. Our acoustic measurements demonstrate unambiguously the emergence of multiple corner states in the middle of the gap, as predicted by the quantized multipole chiral numbers. Our study may provoke new possibilities for controlling sound, such as acoustic sensing and energy trapping.