A random phase approximation study of one-dimensional fermions after a quantum quench

TL;DR

This study uses the random-phase-approximation to analyze how interactions affect one-dimensional fermions in non-equilibrium steady states after a quantum quench, revealing different collective mode behaviors for attractive and repulsive interactions.

Contribution

It provides a novel RPA-based analysis of non-equilibrium fermionic systems post-quench, highlighting the impact of interaction type on collective excitations.

Findings

Attractive interactions lead to over-damped collective modes.

Repulsive interactions support undamped modes above the particle-hole continuum.

The results depend on the nature of the non-equilibrium steady state.

Abstract

The effect of interactions on a system of fermions that are in a non-equilibrium steady state due to a quantum quench is studied employing the random-phase-approximation (RPA). As a result of the quench, the distribution function of the fermions is highly broadened. This gives rise to an enhanced particle-hole spectrum and over-damped collective modes for attractive interactions between fermions. On the other hand, for repulsive interactions, an undamped mode above the particle-hole continuum survives. The sensitivity of the result on the nature of the non-equilibrium steady state is explored by also considering a quench that produces a current carrying steady-state.