Direct measurement of coherent subterahertz acoustic phonons mean free path in GaAs

TL;DR

This paper directly measures the mean free path of coherent subterahertz acoustic phonons in GaAs, revealing a plateau in attenuation that suggests a breakdown of Herring processes at high frequencies.

Contribution

It provides the first direct experimental measurement of phonon mean free path in GaAs at THz frequencies and low temperatures, challenging existing models.

Findings

Observation of a plateau in phonon attenuation above 0.4 THz

Evidence for breakdown of Herring processes at high frequencies

Enhanced understanding of phonon transport in GaAs

Abstract

Phonon mean free path is generally inferred from the measurement of thermal conductivity and we are still lacking precise information on this quantity. Recent advances in the field of high frequency phonons transduction using semiconductor superlattices give the opportunity to fill this gap. We present experimental results on the attenuation of longitudinal acoustic phonons in GaAs in the frequency and temperature ranges 0.2-1THz and 10-80K respectively. Surprisingly, we observe a plateau, in the frequency dependence of the attenuation, above 0.4THz, that we ascribe to a breakdown of Herring processes.