Quantum transport in mesoscopic $^3$He films: experimental study of the interference of bulk and boundary scattering

TL;DR

This study investigates how boundary and bulk scattering interfere to affect quantum transport in $^3$He films, revealing temperature-dependent relaxation times and the influence of surface roughness on quasiparticle scattering.

Contribution

It introduces a quasiclassical model linking surface roughness to effective disorder, validated by experiments, advancing understanding of quantum size effects in $^3$He films.

Findings

Interference between elastic and inelastic scattering explains anomalous temperature dependence.

Surface roughness characterized by a power spectrum impacts quasiparticle scattering.

Elastic scattering centers confirm the model's predictions.

Abstract

We discuss the mass transport of a degenerate Fermi liquid $^3$He film over a rough surface, and the film momentum relaxation time, in the framework of theoretical predictions. In the mesoscopic r\'egime, the anomalous temperature dependence of the relaxation time is explained in terms of the interference between elastic boundary scattering and inelastic quasiparticle-quasiparticle scattering within the film. We exploit a quasiclassical treatment of quantum size effects in the film in which the surface roughness, whose power spectrum is experimentally determined, is mapped into an effective disorder potential within a film of uniform thickness. Confirmation is provided by the introduction of elastic scattering centres within the film. We model further studies on $^3$He confined in nanofluidic sample chambers with lithographically defined surface roughness. The improved understanding of surface roughness scattering may impact on enhancing the conductivity in thin metallic films.