Topological Phononic Crystals with One-Way Elastic Edge Waves

TL;DR

This paper introduces topological phononic crystals with non-trivial bandgaps that support protected one-way elastic edge waves, achieved through gyroscopic effects breaking time-reversal symmetry, promising robust waveguides for various technological applications.

Contribution

It demonstrates a new design of phononic crystals with topologically protected edge states using gyroscopic effects, expanding the scope of topological wave phenomena to elastic waves.

Findings

Bulk Chern numbers of 1 and 2 observed

Support for single and multi-mode edge elastic waves

Edge waves are immune to back-scattering

Abstract

We report a new type of phononic crystals with topologically non-trivial bandgaps for both longitudinal and transverse polarizations, resulting in protected one-way elastic edge waves. In our design, gyroscopic inertial effects are used to break the time-reversal symmetry and realize the phononic analogue of the electronic quantum Hall effect. We investigate the response of both hexagonal and square gyroscopic lattices and observe bulk Chern number of 1 and 2, indicating that these structures support single and multi-mode edge elastic waves immune to back-scattering. These robust one-way phononic waveguides could potentially lead to the design of a novel class of surface wave devices that are widely used in electronics, telecommunication and acoustic imaging.