Anharmonic decay of subterahertz coherent acoustic phonons in GaN

Abstract

This letter examines the anharmonic decay in GaN of subthermal (ℏω⪡kBT) coherent longitudinal acoustic (LA) phonons with a frequency in the subterahertz range. In a collisionless regime (ωτ>1), the anharmonic decay rate of subterahertz coherent LA phonons in GaN shows square dependence on the phonon frequency and cubic dependence on the crystal temperature. As confirmed by the authors experiments, this behavior agrees with a model based on Herring scattering, indicating its importance for the estimation of acoustic attenuation in the subterahertz range.