Snake instability of dark solitons across the BEC-BCS crossover: an effective field theory perspective

TL;DR

This paper investigates the snake instability of dark solitons in superfluid Fermi gases across the BEC-BCS crossover using an effective field theory, analyzing stability and effects of spin-imbalance.

Contribution

It applies a recently developed effective field theory to study dark soliton stability and the influence of spin-imbalance across different interaction regimes.

Findings

Identifies the instability spectra for various interaction regimes.

Estimates the maximum size for stable atomic clouds.

Finds that spin-imbalance stabilizes dark solitons.

Abstract

In the present article the snake instability mechanism for dark solitons in superfluid Fermi gases is studied in the context of a recently developed effective field theory [Eur. Phys. J. B 88, 122 (2015)]. This theoretical treatment has proven to be suitable to study stable dark solitons in quasi-1D setups across the BEC-BCS crossover. In this manuscript the nodal plane of the stable soliton solution is perturbed by adding a transverse modulation. The numerical solution of the system of coupled nonlinear differential equations describing the amplitude of the perturbation leads to the instability spectra which are calculated for a wide range of interaction regimes and compared to other theoretical predictions. The maximum transverse size that the atomic cloud can have in order to preserve the stability is estimated, and the effects of spin-imbalance on this critical length are examined, revealing a stabilization of the soliton with increasing imbalance.