# Topological acoustics

## TL;DR

Topological acoustics explores designing sound-manipulating structures with robust properties using topological principles, advancing novel phases and applications in acoustic systems.

## Contribution

This review surveys fundamental mechanisms, designs, and realizations of topological phases in acoustic systems, highlighting recent advances and future directions.

## Key findings

- Demonstration of topological phases in acoustic metamaterials
- Realization of novel topological semimetal phases in acoustics
- Potential applications in robust sound manipulation

## Abstract

Topological acoustics is an emerging field that lies at the intersection of condensed matter physics, mechanical structural design and acoustics engineering. It explores the design and construction of novel artificial structures, such as acoustic metamaterials and phononic crystals, to manipulate sound waves robustly, taking advantage of topological protection. Early work on topological acoustics was limited to duplicating topological phases that have been understood in condensed matter systems, but recent advances have shifted the paradigm to exploring novel topological concepts that are difficult to realize in other physical systems, such as various topological semimetal phases, and topological phases associated with Floquet engineering, fragile topology, non-Hermiticity and synthetic dimensions. These developments demonstrate the unique advantages of topological acoustic systems and their role in developing topological physics. In this Review, we survey the fundamental mechanisms, basic designs and practical realizations of topological phases in acoustic systems, and provide an overview of future directions and potential applications.