Surface electron mobility over a helium film

TL;DR

This paper evaluates the surface electron mobility over helium films by solving kinetic equations, highlighting interface roughness as the dominant scattering process and comparing results with experimental data.

Contribution

It introduces a comprehensive model incorporating scattering by gas atoms, ripplons, and interface roughness to explain electron mobility over helium films.

Findings

Interface roughness dominates scattering processes.

Model matches experimental mobility data.

Estimated substrate defect sizes using Gaussian roughness model.

Abstract

The mobility of surface electrons localized over helium films underlying solid substrates has been evaluated by solving the Boltzmann equation in the time relaxation approximation and the force balance equation in which an effective mobility is obtained in terms of the dynamical structure factor of the nondegenerate electron liquid. The essential processes of electron scattering by gas atoms, ripplons, and film-solid interface roughness are taken into account. The electron mobility dependence on the film thickness and temperature is determined and compared with experimental data available. We find that the interface-roughness scattering is the dominant process for explaining the experimental results. We estimate the extended defect sizes of the underlying substrate within the Gaussian correlated model for interface roughness.