Dynamics of a quantum quench in an ultra-cold atomic BCS superfluid

TL;DR

This paper investigates the non-equilibrium dynamics of an ultra-cold atomic BCS superfluid as it approaches a quantum critical point, revealing distinct stages of evolution and critical behavior in the gap and Cooper pair size.

Contribution

It provides a detailed analysis of the non-equilibrium evolution and critical properties of the BCS superfluid near the quantum critical point, highlighting three distinct dynamical stages.

Findings

Identification of three stages: adiabatic, weakly non-equilibrium, strongly non-equilibrium.

Demonstration that Cooper pair size reflects critical properties during the transition.

Observation of decoupling of pair size from gaps in the strongly non-equilibrium regime.

Abstract

We study dynamics of an ultra-cold atomic BCS superfluid driven towards the BCS superfluid-Fermi liquid quantum critical point by a gradual decrease of the pairing interaction. We analyze how the BCS superfluid falls out of equilibrium and show that the non-equilibrium gap and Cooper pair size reflect critical properties of the transition. We observe three stages of evolution: adiabatic where the Cooper pair size is inversely proportional to the equilibrium gap, weakly non-equilibrium where it is inversely proportional to the non-equilibrium gap, and strongly non-equilibrium where it decouples from both equilibrium and non-equilibrium gap. These phenomena should stimulate future experimental characterization of non-equilibrium ultra-cold atomic BCS superfluids.