Oscillating Solitons and AC Josephson Effect in Ferromagnetic Bose-Bose Mixtures

TL;DR

This paper predicts that in a two-component Bose-Einstein condensate near the demixing transition, dark-bright solitons should oscillate under a constant force, demonstrating a spin-Josephson effect with potential experimental realization.

Contribution

It introduces a novel prediction of oscillating solitons in ferromagnetic Bose mixtures and links this to a spin-Josephson effect, providing a new perspective on BEC dynamics.

Findings

Dark-bright solitons oscillate under a constant force.

Mapping to Landau-Lifshitz equation predicts this oscillation.

Proposes an experimental setup to observe the effect.

Abstract

Close to the demixing transition, the degree of freedom associated to relative density fluctuations of a two-component Bose-Einstein condensate is described by a non-dissipative Landau-Lifshitz equation. In the quasi one-dimensional weakly immiscible case, this mapping surprisingly predicts that a dark-bright soliton should oscillate when subject to a constant force favoring separation of the two components. We propose a realistic experimental implementation of this phenomenon which we interpret as a spin-Josephson effect in the presence of a movable barrier.