Diffusive density profiles in a cold-atom expansion experiment

TL;DR

This paper shows that the observed density profiles in a cold-atom expansion experiment can be explained by slow diffusion with energy-dependent coefficients, challenging the previous interpretation based on Anderson localization.

Contribution

It demonstrates that slow diffusion with an energy-dependent diffusion coefficient can account for experimental density profiles, providing an alternative to Anderson localization explanations.

Findings

Density profiles match diffusion model predictions

Diffusion coefficient depends on particle energy

Challenges the localization interpretation in the experiment

Abstract

In a recent experiment [McGehee et al., Phys. Rev. Lett. 111, 145303 (2013)], the expansion of non-interacting ultracold fermions was studied in a random speckle potential, and the observed density profiles were interpreted based on 3D Anderson localization. The purpose of this note is to demonstrate that slow diffusion of particles with a broad energy distribution and an energy-dependent diffusion coefficient leads to density profiles that agree with the measured data, but not with the behavior expected for 3D Anderson localization.