Steady-state properties of a thermodynamically unbalanced Fermi gas

TL;DR

This paper investigates the steady-state properties of a non-equilibrium Fermi gas in a metallic wire, revealing how response functions, correlations, and entanglement entropy behave differently from equilibrium, with implications for universal quantities.

Contribution

It provides a detailed analysis of the spectral function, dynamical structure factor, and entanglement entropy in a non-equilibrium Fermi gas, highlighting non-equilibrium signatures and the breakdown of universal equilibrium properties.

Findings

Spectral function and structure factor show non-equilibrium signatures.

Entanglement entropy is extensive with voltage-dependent logarithmic corrections.

Universal quantities in equilibrium do not persist out of equilibrium.

Abstract

The current-carrying steady-state that arises in the middle of a metallic wire connected to macroscopic leads is characterized regarding its response functions, correlations and entanglement entropy. The spectral function and the dynamical structure factor show clear non-equilibrium signatures accessible by state-of-the-art techniques. In contrast with the equilibrium case, the entanglement entropy is extensive with logarithmic corrections at zero-temperature that depend on the wire-leads coupling and, in a non-analytic way, on voltage. This shows that some robust universal quantities found in gapless equilibrium phases do not persist away from equilibrium.