Breakdown of Herring's processes in cubic semiconductors for sub-terahertz longitudinal acoustic phonons

TL;DR

This paper explains the anomalous attenuation plateau of longitudinal acoustic phonons in GaAs at sub-terahertz frequencies through ab initio calculations, revealing the competition of phonon-phonon scattering mechanisms and predicting similar behavior in silicon.

Contribution

It provides a detailed theoretical explanation for the attenuation plateau in cubic semiconductors using ab initio methods, linking it to phonon scattering mechanisms.

Findings

Attenuation plateau observed between 0.6 and 1 GHz in GaAs.

Agreement between experimental measurements and ab initio calculations.

Prediction of similar scattering behavior in silicon at 1.2-1.7 THz.

Abstract

In the present work we explain the anomalous behavior of the attenuation of the longitudinal acoustic phonon in GaAs as a function of the phonon energy $\omega$ in the sub-THz domain. These attenuations along the [100] direction show a plateau between 0.6 and 1 GHz at low temperatures. We found an excellent agreement between measurements performed by some of us, and new \textit{ab initio} calculations of third-order anharmonic processes. The formation of the plateau is explained by the competition between different phonon-phonon scattering processes as Herring's mechanism, which dominates at low frequencies, saturates and disappears. The plateau is shown to be determined by the phononic final-state phase-space available at a given temperature. We predict that a change of scattering mechanism should also show up in the attenuation of silicon around 1.2-1.7 THz, and argue that the attenuation plateau is a general feature of cubic semiconductors.