Observation of topological edge modes in a quasi-periodic acoustic waveguide

TL;DR

This paper demonstrates the creation and observation of topological edge modes in a quasi-periodic acoustic waveguide, combining theoretical calculations with experimental validation.

Contribution

It introduces a simple wall patterning method to generate topological boundary modes and computes the bulk invariant for the continuum wave equation.

Findings

Topological gaps are opened in the acoustic spectrum.

Experimental measurements match theoretical predictions.

High Q-factor localized acoustic modes are achieved.

Abstract

Topological boundary and interface modes are generated in an acoustic waveguide by simple quasi-periodic patternings of the walls. The procedure opens many topological gaps in the resonant spectrum and qualitative as well as quantitative assessments of their topological character are supplied. In particular, computations of the bulk invariant for the continuum wave equation are performed. The experimental measurements reproduce the theoretical predictions with high fidelity. In particular, acoustic modes with high Q-factors localized in the middle of a breathable waveguide are engineered by a simple patterning of the walls.