Collective Excitations and Nonequilibrium Phase Transition in Dissipative Fermionic Superfluids

TL;DR

This paper predicts a novel mechanism where sudden two-body loss induces collective excitations and a nonequilibrium phase transition in fermionic superfluids, extending BCS theory to account for particle loss.

Contribution

It introduces a new theoretical framework for understanding dissipation effects in fermionic superfluids, revealing dissipation-induced collective modes and phase transitions.

Findings

Dissipation causes amplitude oscillations and phase rotation in superfluid order parameter.

A nonequilibrium phase transition occurs with vanishing Josephson current.

The phenomena can be realized in ultracold fermionic atom experiments.

Abstract

We predict a new mechanism to induce collective excitations and a nonequilibrium phase transition of fermionic superfluids via a sudden switch-on of two-body loss, for which we extend the BCS theory to fully incorporate a change in particle number. We find that a sudden switch-on of dissipation induces an amplitude oscillation of the superfluid order parameter accompanied by a chirped phase rotation as a consequence of particle loss. We demonstrate that when dissipation is introduced to one of the two superfluids coupled via a Josephson junction, it gives rise to a nonequilibrium dynamical phase transition characterized by the vanishing dc Josephson current. The dissipation-induced collective modes and nonequilibrium phase transition can be realized with ultracold fermionic atoms subject to inelastic collisions.