Optically Controlled Topologically Protected Acoustic Wave Amplification

Abstract

Acoustic topological insulators that lead to backscattering-immune edge states provide an important way to control and manipulate the behaviors of phonons. To date, most of these acoustic systems are based on single-particle Hamiltonians that conserve particle number. Here, we exploit particle-nonconserving phonon–photon interactions to engineer not only the band structure but also the dissipation of acoustic waves. We find a topologically protected edge state for phonons that can be parametrically amplified while all the bulk modes remain stable. This phenomenon can be exploited to realize topologically protected nonreciprocal traveling-wave amplification for phonons, which may find wide applications in classical and quantum acoustics.