Shear viscosity and spin diffusion in a two-dimensional Fermi gas

TL;DR

This paper studies how shear viscosity and spin diffusion vary with temperature in a two-dimensional Fermi gas, incorporating medium effects to improve accuracy and comparing results with experimental data.

Contribution

It provides a comprehensive numerical analysis of transport coefficients in a 2D Fermi gas, including medium effects, and aligns theoretical predictions with recent experimental measurements.

Findings

Medium effects reduce η/s and spin diffusion by a factor of three.

Trap-averaged viscosity matches recent experimental results.

Numerical solutions of the Boltzmann equation enhance understanding of transport in 2D Fermi gases.

Abstract

We investigate the temperature dependence of the shear viscosity and spin diffusion in a two-dimensional Fermi gas with contact interactions, as realized in ultra-cold atomic gases. We describe the transport coefficients in terms of a Boltzmann equation and present a full numerical solution for the degenerate gas. In contrast to previous works we take the medium effects due to finite density fully into account. This effect reduces the viscosity to entropy ratio, $\eta/s$, by a factor of three, and similarly for spin diffusion. The trap averaged viscosity agrees well with recent measurements by Vogt et al. [Phys. Rev. Lett. 108, 070404 (2012)].