Merging and oscillations of dipolar Bose-Einstein condensate droplets

TL;DR

This paper studies the dynamics and phase diagrams of dipolar Bose-Einstein condensate droplets in a double-well potential, revealing oscillations, mergers, and symmetry-breaking phenomena through numerical solutions of the dipolar Gross-Pitaevskii equation.

Contribution

It provides new insights into the time evolution, oscillations, and merging behavior of dipolar BEC droplets, including the effects of atom number and interaction strength.

Findings

Droplet oscillations are driven by external potential and dipolar tails.

Droplet mergers occur when initial energy surpasses the interdroplet barrier.

Oscillations and atom leakage contribute to damping over time.

Abstract

We investigate the dynamics of Bose-Einstein condensate droplets composed of $^{164}$Dy atoms formed in a double-well potential following removal of the interwell barrier. By solving the dipolar Gross-Pitaevskii equation, we determine phase diagrams of ground-state configurations as functions of the atom number confined in the double-well potential. For strong dipolar interactions, some of the lowest-energy configurations arise from spontaneous symmetry breaking of the droplet structure, which optimizes the interaction energy. We analyze the subsequent time evolution after removal of the central barrier, revealing both droplet oscillations and merger events leading to the formation of larger droplets. The oscillations are driven by the external potential and by the repulsive tails of the in-plane component of the dipolar interaction. Merger events occur when the initial excess energy is sufficient to overcome the interdroplet potential barrier. The oscillatory dynamics depend sensitively on the atom number, the strength of dipolar interactions, and the initial symmetry of the configuration. We find that both oscillations of individual droplets and atom leakage from the droplets, induced by close droplet-droplet encounters, contribute to the damping of the oscillations.