Resonance-like piezoelectric electron-phonon interaction in layered structures

TL;DR

This paper demonstrates that mismatch in piezoelectric parameters in layered quantum structures enhances electron-phonon interactions, enabling collimated high-frequency phonon emission, which explains recent experimental observations in GaAs/AlAs superlattices.

Contribution

It reveals a resonance-like electron-phonon interaction mechanism in layered structures due to piezoelectric mismatch, leading to efficient phonon emission.

Findings

Short-wavelength phonons induce strong piezo-potential components.

Enhanced electron-phonon interaction causes collimated phonon beams.

Experimental evidence supports the proposed mechanism.

Abstract

We show that mismatch of the piezoelectric parameters between layers of multiple-quantum well structures leads to modification of the electron-phonon interaction. In particular, short-wavelength phonons propagating perpendicular to the layers with wavevector close to $2\pi n/d$, where $d$ is the period of the structure, induce a strong smoothly-varying component of the piezo-potential. As a result, they interact efficiently with 2D electrons. It is shown, that this property leads to emission of collimated quasi-monochromatic beams of high-frequency acoustic phonons from hot electrons in multiple-quantum well structures. We argue that this effect is responsible for the recently reported monochromatic transverse phonon emission from optically excited GaAs/AlAs superlattices, and provide additional experimental evidences of this.