Tunable Acoustic Valley-Hall Edge States in Reconfigurable Phononic Elastic Waveguides

TL;DR

This paper demonstrates tunable acoustic topological edge states in reconfigurable 2D phononic waveguides, showing how strain-induced symmetry breaking creates protected edge modes with potential for adaptive wave control.

Contribution

It introduces a method to induce and tune topological edge states in elastic waveguides via strain, enabling reconfigurable acoustic topological insulators.

Findings

Topological transition occurs with strain-induced symmetry breaking.

Edge states are protected when inter-valley mixing is weak.

Strain modulation allows dynamic tuning of edge state responses.

Abstract

This study investigates the occurrence of acoustic topological edge states in a 2D phononic elastic waveguide due to a phenomenon that is the acoustic analogue of the quantum valley Hall effect. We show that a topological transition takes place between two lattices having broken space inversion symmetry due to the application of a tunable strain field. This condition leads to the formation of gapless edge states at the domain walls, as further illustrated by the analysis of the bulk-edge correspondence and of the associated topological invariants. Although time reversal symmetry is still intact in these systems, the edge states are topologically protected when inter-valley mixing is either weak or negligible. Interestingly, topological edge states can also be triggered at the boundary of a single domain if boundary conditions are properly selected. We also show that the static modulation of the strain field allows tuning the response of the material between the different supported edge states.