Density-and-phase domain walls in a condensate with dynamical gauge potentials

TL;DR

This paper demonstrates how to create and analyze density-and-phase domain walls in a Bose-Einstein condensate influenced by dynamical gauge potentials, revealing their formation, stability, and relation to synthetic electromagnetic fields.

Contribution

It introduces a method to generate and study domain walls in condensates with density-dependent gauge potentials, highlighting the roles of vector and scalar potentials in their formation.

Findings

Domain walls separate high- and low-density regions with opposite momenta.

Repulsive interactions enhance the prominence of domain walls.

A first-order phase transition leads to metastability at strong electric fields.

Abstract

We show how one can generate domain walls that separate high- and low-density regions with opposite momenta in the ground state of a harmonically trapped Bose-Einstein condensate using a density-dependent gauge potential. Within a Gross-Pitaevskii framework, we elucidate the distinct roles of vector and scalar potentials and how they lead to synthetic electromagnetic fields that are localized at the domain wall. In particular, the kinetic energy cost of a steep density gradient is compensated by an electrostatic field that pushes particles away from a special value of density. We show numerically in one dimension that such a domain wall is more prominent for repulsive contact interactions, and becomes metastable at strong electric fields through a first-order phase transition that ends at a critical point as the field is reduced. Our findings build on recent experimental developments and may be realized with cold atoms in a shaken optical lattice, providing insights into collective phenomena arising from dynamical gauge fields.