Dynamical vanishing of the order parameter in a fermionic condensate

TL;DR

This paper studies the non-equilibrium dynamics of a fermionic superfluid after a sudden change in pairing strength, revealing a critical point where the order parameter vanishes and the system exhibits mixed properties.

Contribution

It provides an exact analysis of the long-time behavior of a fermionic condensate after a quench, identifying a critical pairing strength where superfluid order disappears.

Findings

Order parameter asymptotes to a constant value

Order parameter vanishes below a critical pairing strength

Steady state exhibits mixed normal and superfluid properties

Abstract

We analyze the dynamics of a condensate of ultra-cold atomic fermions following an abrupt change of the pairing strength. At long times, the system goes to a non-stationary steady state, which we determine exactly. The superfluid order parameter asymptotes to a constant value. We show that the order parameter vanishes when the pairing strength is decreased below a certain critical value. In this case, the steady state of the system combines properties of normal and superfluid states - the gap and the condensate fraction vanish, while the superfluid density is nonzero.