An atomic bright vector soliton as an active particle

TL;DR

This paper demonstrates a mechanism for creating an active particle using a vector bright soliton in a Bose-Einstein condensate, enabling motion against external forces by internal energy transfer.

Contribution

It introduces a dynamical energy transfer mechanism within a spinor condensate to turn a vector bright soliton into an active particle, extending the concept beyond simple models.

Findings

The energy transfer mechanism enables soliton motion against external forces.

The mechanism is robust under various deformations of the model.

Experimental feasibility is demonstrated within a spinor condensate system.

Abstract

Solitons in general are configurations of extended fields which move like isolated particles. Vector bright solitons can occur in a two-component self-attractive Bose-Einstein condensate. If the components of the condensate have different chemical potentials, the total spin of the soliton can serve as an internal energy depot that makes the soliton into an \emph{active} particle, able to move against an external force using energy carried within the particle -- if there is a dynamical mechanism for steadily transferring energy from soliton spin into soliton motion. Here we present such a dynamical mechanism, embed it in an experimentally feasible way within the larger system of a spinor condensate mean field, and show how the mechanism works to realize a solitonic active particle. In what can be considered a toy model for the project of going beyond toy models for active particles, we test the robustness of the activity mechanism by exploring a range of deformations to the simplest model for embedding the nonlinear mechanism in the condensate system.