Dynamical pattern formation during growth of a dual-species Bose-Einstein condensate

TL;DR

This paper simulates the growth of a dual-species Bose-Einstein condensate, revealing complex pattern formation due to modulation instability, and compares the results with experimental observations.

Contribution

It introduces a simulation approach for condensate growth that captures dynamic pattern formation, aligning well with recent experimental findings.

Findings

Formation of interleaved bubble patterns during growth

Pattern influenced by modulation instability

Final state differs from the ground state in phase-separated systems

Abstract

We simulate the growth of a dual species Bose-Einstein condensate using a Gross-Pitaevskii equation with an additional gain term giving rise to the growth. Such growth occurs during simultaneous evaporative cooling of a mixture of two gases. The ground state of a dual condensate is normally either a miscible mixture, or an immiscible phase with two spatially separated components. In a cigar trap the ground state typically consists of one component in the center, and the other component flanking it. Our simulations show that when the condensates are formed in a cigar trap and the mixture is phase separated, then the final state upon the end of the growth is generally far from the true ground state of the system. Instead it consists of multiple, interleaved bubbles of the two species. Such a pattern was observed recently in an experiment by Wieman's group at JILA, and our simulations are in good qualitative agreement with the experiment. We explain the pattern formation as due to the onset of modulation instability during growth, and study the dependence of the final state pattern on various parameters of the system.