Topological Sound

TL;DR

This paper reviews recent advances in topological acoustics, highlighting how sound waves can exhibit topologically protected states similar to quantum systems, despite unique challenges like the lack of intrinsic spin polarization.

Contribution

It provides a comprehensive overview of theoretical and experimental progress in realizing topological states of sound in 2D and 3D systems, emphasizing spin and valley degrees of freedom.

Findings

Demonstration of one-way edge modes in acoustic systems

Experimental verification of defect-immune sound propagation

Theoretical models explaining topological sound states

Abstract

Recently, we witnessed a tremendous effort to conquer the realm of acoustics as a possible playground to test with sound waves topologically protected wave propagation. Acoustics differ substantially from photonic and electronic systems since longitudinal sound waves lack intrinsic spin polarization and breaking the time-reversal symmetry requires additional complexities that both are essential in mimicking the quantum effects leading to topologically robust sound propagation. In this article, we review the latest efforts to explore with sound waves topological states of quantum matter in two- and three-dimensional systems where we discuss how spin and valley degrees of freedom appear as highly novel ingredients to tailor the flow of sound in the form of one-way edge modes and defect-immune protected acoustic waves. Both from a theoretical stand point and based on contemporary experimental verifications, we summarize the latest advancements of the flourishing research frontier on topological sound.