Dynamical Phase Transition of Dissipative Fermionic Superfluids

TL;DR

This paper uncovers a new type of dynamical phase transition in dissipative fermionic superfluids, where the superfluid order parameter vanishes abruptly due to inelastic scattering, revealing unique transient behaviors in open quantum systems.

Contribution

It introduces a generalized time-dependent Hartree-Fock-Bogoliubov framework for open systems and demonstrates a novel dynamical phase transition characterized by non-analytic order parameter decay.

Findings

Superfluid order parameter vanishes non-analytically at a critical time.

Discontinuous change in the first derivative of the superfluid fraction.

Dynamical phase transition occurs without fine-tuning of initial states.

Abstract

Driven-dissipative open quantum many-body systems exhibit rich phases that are characterized by the steady states in the long-time dynamics. However, lossy open systems inevitably decay to the vacuum, making their transient evolution the primary focus. Assuming the Hartree-Fock-Bogoliubov ansatz, we derive a generalized time-dependent Hartree-Fock-Bogoliubov equation based on the least action principle for open quantum systems. By solving the quench dynamics after abruptly introducing inelastic scattering or one-body loss in the Bardeen-Cooper-Schrieffer limit, we reveal a generic dynamical phase transition: the superfluid order parameter vanishes non-analytically while the superfluid fraction's first-order time derivative undergoes a discontinuous change at a finite critical time. This marks a new paradigm of dynamical phase transitions, distinct from those in closed systems, where the initial state must be finely tuned.