Dark-Bright Solitons in a Superfluid Bose-Fermi Mixture

TL;DR

This paper theoretically investigates dark-bright solitons in a superfluid Bose-Fermi mixture, revealing that in the partially separated phase, a dark soliton in the Fermi superfluid is accompanied by a broad bosonic component, forming a coherent dark-bright soliton.

Contribution

It introduces the concept of dark-bright solitons in Bose-Fermi mixtures and analyzes their properties in the partially separated phase.

Findings

Dark-bright solitons form in the partially separated phase.

The bosonic component broadens and coexists with the fermionic dark soliton.

The soliton maintains full spatial coherence.

Abstract

The recent experimental realization of Bose-Fermi superfluid mixtures of dilute ultracold atomic gases has opened new perspectives in the study of quantum many-body systems. Depending on the values of the scattering lengths and the amount of bosons and fermions, a uniform Bose-Fermi mixture is predicted to exhibit a fully mixed phase, a fully separated phase or, in addition, a purely fermionic phase coexisting with a mixed phase. The occurrence of this intermediate configuration has interesting consequences when the system is nonuniform. In this work we theoretically investigate the case of solitonic solutions of coupled Bogoliubov-de Gennes and Gross-Pitaevskii equations for the fermionic and bosonic components, respectively. We show that, in the partially separated phase, a dark soliton in Fermi superfluid is accompanied by a broad bosonic component in the soliton, forming a dark-bright soliton which keeps full spatial coherence.