Quantum transport in strongly correlated Fermi gases

TL;DR

This paper develops a theoretical framework for quantum transport in strongly correlated Fermi gases, emphasizing the role of pair correlations in transport coefficients and their experimental measurement.

Contribution

It introduces a new approach that incorporates local fermion pair correlations into quantum transport theory, highlighting their impact on viscosity and thermal transport.

Findings

Pair excitations dominate bulk viscosity.

Transport coefficients can be measured via scattering length response.

System relaxes to hydrodynamic behavior after out-of-equilibrium perturbations.

Abstract

Transport in strongly correlated fermions cannot be understood by fermionic quasiparticles alone. We present a theoretical framework for quantum transport that incorporates strong local correlations of fermion pairs. These contact correlations add essential contributions to viscous, thermal and sound transport coefficients. The bulk viscosity, in particular, receives its dominant contribution from pair excitations. Moreover, it can be measured elegantly by observing the response to a time-dependent scattering length even when the fluid is not moving. Rapid changes of the scattering length drive the system far out of local equilibrium, and we show how it relaxes back to equilibrium following a hydrodynamic attractor before a Navier-Stokes description becomes valid.