Non-thermal equilibration of a one-dimensional Fermi gas

TL;DR

This paper investigates how a one-dimensional Fermi gas reaches equilibrium after an interaction quench, revealing both thermal and nonthermal states with specific momentum distribution features.

Contribution

It introduces a nonperturbative approach using Kadanoff-Baym equations to study the equilibration process in a 1D Fermi gas.

Findings

High-momentum tails follow power laws near Fermi temperature

Distributions show Fermi-Dirac form at lower momenta

Nonthermal states characterized by fluctuation-dissipation relations

Abstract

Equilibration of an isolated Fermi gas in one spatial dimension after an interaction quench is studied. Evaluating Kadanoff-Beym dynamic equations for correlation functions obtained from the two-particle-irreducible effective action in nonperturbative approximation, the gas is seen to evolve to states characterized by thermal as well as nonthermal momentum distributions, depending on the assumed initial conditions. For total energies near the Fermi temperature, stationary power laws emerge for the high-momentum tails while at lower momenta the distributions are of Fermi-Dirac type. The relation found between fluctuations and dissipation exhibits nonthermal final states.