The decay and collisions of dark solitons in superfluid Fermi gases

TL;DR

This paper investigates how dark solitons in superfluid Fermi gases decay and collide across the BEC-BCS crossover, revealing increased inelasticity and sound emission as the system moves from BEC to BCS regimes.

Contribution

It provides a detailed numerical analysis of soliton decay and collision dynamics across the BEC-BCS crossover using Bogoliubov-de Gennes equations, highlighting the role of Andreev bound states.

Findings

Soliton decay into sound occurs when accelerated to pair-breaking speed.

Collisions become more inelastic from BEC to BCS regimes.

Excess energy from inelastic collisions converts into sound.

Abstract

We study soliton collisions and the decay of solitons into sound in superfluid Fermi gases across the Bose-Einstein condensate to Bardeen-Cooper-Schrieffer (BEC-BCS) crossover by performing numerical simulations of the time-dependent Bogoliubov-de Gennes equations. This decay process occurs when the solitons are accelerated to the bulk pair-breaking speed by an external potential. A similar decay process may occur when solitons are accelerated by an inelastic collision with another soliton. We find that soliton collisions become increasingly inelastic as we move from the BEC to BCS regimes, and the excess energy is converted into sound. We interpret this effect as being due to evolution of Andreev bound states localized within the soliton.