Tunable topological phononic crystals

TL;DR

This paper presents a tunable topological phononic crystal with a Dirac-like cone, demonstrating how breaking time-reversal symmetry and changing unit cell geometry induce topological transitions, verified by Chern number and edge mode analysis.

Contribution

It introduces a phononic crystal with a tunable topological bandgap achieved by breaking time-reversal symmetry and modifying geometry, enabling adaptable acoustic topological insulators.

Findings

Topological transition verified by Chern number calculation.

Edge mode analysis confirms topologically protected states.

Bandgap topology is tunable via velocity field and geometric size.

Abstract

Topological insulators, first observed in electronic systems, have inspired many analogues in photonic and phononic crystals in which remarkable one-way propagation edge states are supported by topologically nontrivial bandgaps. Such bandgaps can be achieved by breaking the time-reversal symmetry to lift the degeneracy associated with Dirac cones at the corners of the Brillouin zone. Here, we report on our construction of a phononic crystal exhibiting a Dirac-like cone in the Brillouin zone center. We demonstrate that simultaneously breaking the time-reversal symmetry and altering the geometric size of the unit cell result in a topological transition that is verified by the Chern number calculation and edge mode analysis. The topology of the bandgap is tunable by varying both the velocity field and the geometric size; such tunability may dramatically enrich the design and use of acoustic topological insulators.