Soliton core filling in superfluid Fermi gases with spin-imbalance

TL;DR

This study investigates dark solitons in spin-imbalanced superfluid Fermi gases across the BEC-BCS crossover using an advanced effective field theory, revealing how population imbalance fills soliton cores with unpaired atoms and affects their dynamics.

Contribution

It applies a novel effective field theory to analyze soliton properties in spin-imbalanced Fermi gases, extending understanding beyond traditional Ginzburg-Landau models.

Findings

Population imbalance fills soliton cores with unpaired atoms.

Core filling alters the soliton's effective mass and dynamical behavior.

Properties of density profiles change across the BEC-BCS crossover.

Abstract

In this paper the properties of dark solitons in superfluid Fermi gases with spin-imbalance are studied by means of a recently developed effective field theory [S. N. Klimin, J. Tempere, G. Lombardi, J. T. Devreese, Eur. Phys. J. B 88, 122 (2015)] suitable to describe the BEC-BCS crossover in ultracold gases in an extended range of temperatures as compared to the usual Ginzburg-Landau treatments. The spatial profiles for the total density and for the density of the excess-spin component, and the changes of their properties across the BEC-BCS crossover are examined in different conditions of temperature and imbalance. The presence of population imbalance is shown to strongly affect the structure of the soliton excitation by filling its core with unpaired atoms. This in turn influences the dynamical properties of the soliton since the additional particles in the core have to be dragged along thus altering the effective mass.