Hydrodynamic Relaxation in a Strongly Interacting Fermi Gas

TL;DR

This paper experimentally investigates the decay of density perturbations in a strongly interacting Fermi gas, enabling direct measurement of thermal conductivity and shear viscosity through analysis of diffusive and sound modes.

Contribution

It introduces a method to measure thermal conductivity and shear viscosity in a strongly interacting Fermi gas via decay of density profiles in a box potential.

Findings

Measured thermal conductivity and shear viscosity directly from decay modes.

Identified exponential decay and oscillatory modes in the density profile.

Provided insights into hydrodynamic relaxation in strongly interacting quantum fluids.

Abstract

We measure the free decay of a spatially periodic density profile in a normal fluid strongly interacting Fermi gas, which is confined in a box potential. This spatial profile is initially created in thermal equilibrium by a perturbing potential. After the perturbation is abruptly extinguished, the dominant spatial Fourier component exhibits an exponentially decaying (thermally diffusive) mode and a decaying oscillatory (first sound) mode, enabling independent measurement of the thermal conductivity and the shear viscosity directly from the time-dependent evolution.