Spin diffusion in trapped clouds of strongly interacting cold atoms

TL;DR

This paper explains recent experimental observations of spin diffusion in strongly interacting cold atomic gases by adapting diffusion models to account for trapping potentials, inhomogeneous diffusion coefficients, and the breakdown of diffusion approximation in low-density regions.

Contribution

It introduces a modified diffusion framework that incorporates trapping potential effects, inhomogeneity, and non-diffusive behavior in dilute regions for strongly interacting atomic gases.

Findings

Modified Fick's law accounts for trapping potential effects.

Inhomogeneous diffusion coefficient due to density variations.

Diffusion approximation fails in low-density outer regions.

Abstract

We show that puzzling recent experimental results on spin diffusion in a strongly interacting atomic gas may be understood in terms of the predicted spin diffusion coefficient for a generic strongly interacting system. Three important features play a central role: a) Fick's law for diffusion must be modified to allow for the trapping potential, b) the diffusion coefficient is inhomogeneous, due to the density variations in the cloud and c) the diffusion approximation fails in the outer parts of the cloud, where the mean free path is long.