Commensurability oscillations in the SAW induced acousto-electric effect in a 2DEG

TL;DR

This paper investigates the acousto-electric effect induced by surface acoustic waves in a high mobility 2D electron gas, revealing Weiss oscillations and resonances related to cyclotron orbits and SAW frequency.

Contribution

It provides a detailed analysis of how Weiss oscillations and resonances manifest in the acousto-electric effect, especially considering small-angle impurity scattering and damping in low magnetic fields.

Findings

Weiss oscillations are periodic in inverse magnetic field due to commensurability.

Resonances occur at SAW frequency multiples of cyclotron frequency.

Oscillations are damped in low fields where cyclotron frequency times scattering time is less than one.

Abstract

We study the acousto-electric (AE) effect generated by surface acoustic waves (SAW) in a high mobility 2D electron gas (2DEG) with isotropic and especially small-angle impurity scattering. In both cases the acousto-electric effect exhibits Weiss oscillations periodic in $B^{-1}$ due to the commensurability of the SAW period with the size of the cyclotron orbit and resonances at the SAW frequency $\omega=k\omega_{c}$ multiple of the cyclotron frequency. We describe how oscillations in the acousto-electric effect are damped in low fields where $\omega_{c}\tau_{\ast}\lesssim1$ (with the time scale $\tau_{\ast}$ dependent on the type of scattering) and find its non-oscillatory part which remains finite to the lowest fields.