Binary Mixtures of Bose-Einstein Condensates: Phase dynamics and Spatial Dynamics

TL;DR

This paper studies the phase coherence and stability of two interacting Bose-Einstein condensates, including particle number fluctuations, providing analytical and numerical insights relevant to recent experiments.

Contribution

It introduces an analytical solution for binary condensate mixtures and analyzes how interaction parameters affect phase coherence times.

Findings

Phase coherence time increases when interaction constants are similar.

Demixing instabilities depend on coupling constants.

Numerical results align with recent experimental parameters.

Abstract

We investigate the relative phase coherence properties and the occurrence of demixing instabilities for two mutually interacting and time evolving Bose-Einstein condensates in traps. Our treatment naturally includes the additional decoherence effect due to fluctuations in the total number of particles. Analytical results are presented for the breathe-together solution, an extension of previously known scaling solution to the case of a binary mixture of condensates. When the three coupling constants describing the elastic interactions among the atoms in the two states are close to each other, a dramatic increase of the phase coherence time is predicted. Numerical results are presented for the parameters of the recent JILA experiments.