Universal Density Shift Coefficients for the Thermal Conductivity and Shear Viscosity of a Unitary Fermi Gas

Abstract

We measure universal temperature-independent density shifts for the thermal conductivity $\kappa_T$ and shear viscosity $\eta$, relative to the high temperature limits, for a normal phase unitary Fermi gas confined in a box potential. We show that a time-dependent kinetic theory model enables extraction of the hydrodynamic transport times $\tau_\eta$ and $\tau_\kappa$ from the time-dependent free-decay of a spatially periodic density perturbation, yielding the static transport properties and density shifts, corrected for finite relaxation times.