Medium effects and the shear viscosity of the dilute Fermi gas away from the conformal limit

Abstract

We study the shear viscosity of a dilute Fermi gas as a function of the scattering length in the vicinity of the unitarity limit. The calculation is based on kinetic theory, which provides a systematic approach to transport properties in the limit in which the fugacity $z=n{\lambda }^3/2$ is small. Here, $n$ is the density of the gas and $\lambda$ is the thermal wave length of the fermions. At leading order in the fugacity expansion the shear viscosity is independent of density, and the minimum shear viscosity is achieved at unitarity. At the next order medium effects modify the scattering amplitude as well as the quasi-particle energy and velocity. We show that these effects shift the minimum of the shear viscosity to the Bose-Einstein condensation (BEC) side of the resonance, in agreement with the result of recent experiments.

arXiv commentOct 10, 2014. 17 pp

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• The BCS-BEC crossover: From ultra-cold Fermi gases to nuclear systems
• Observation of the Leggett-Rice effect in a unitary Fermi gas
• Model-independent determination of the shear viscosity of a trapped unitary Fermi gas: Application to high temperature data
• Perfect-fluid behavior of a dilute Fermi gas near unitary
• Numerical solution of the Boltzmann equation for trapped Fermi gases with in-medium effects
• Mesoscopic dynamics of fermionic cold atoms ---Quantitative analysis of transport coefficients and relaxation times---
• Shear viscosity and Strong-Coupling Corrections in the BCS-BEC crossover Regime of an Ultracold Fermi Gas
• Shear Viscosity of Uniform Fermi Gases with Population Imbalance
• Kovtun-Son-Starinets Conjecture and Effects of Mass Imbalance in the Normal State of an Ultracold Fermi Gas in the BCS-BEC Crossover Region
• Finite Temperature Behaviors of q-deformed Fermi Gases