# Zone folding induced topological insulators in phononic crystals

## TL;DR

This paper demonstrates a novel method to create acoustic topological insulators in phononic crystals using zone folding and lattice symmetry breaking, enabling robust one-way sound propagation for noise control and waveguides.

## Contribution

It introduces a zone folding strategy from photonics to phononic crystals to realize topological insulators with experimentally verified robust sound transport.

## Key findings

- Successful formation of double Dirac cones in phononic crystals
- Experimental demonstration of robust one-way sound propagation
- Potential applications in noise control and waveguide design

## Abstract

This letter investigates a flow-free, pseudospin-based acoustic topological insulator. Zone folding, a strategy originated from photonic crystal, is used to form double Dirac cones in phononic crystal. The lattice symmetry of the phononic crystal is broken by tuning the size of the center "atom" of the unit cell in order to open the nontrivial topological gap. Robust sound one-way propagation is demonstrated both numerically and experimentally. This study provides a flexible approach for realizing acoustic topological insulators, which are promising for applications such as noise control and waveguide design.