Phase dynamics after connection of two separate Bose-Einstein condensates

TL;DR

This paper investigates the phase dynamics of two connected Bose-Einstein condensates, revealing rapid decoherence, quasiparticle creation, and a transition from quantum to semiclassical behavior characterized by Josephson oscillations.

Contribution

It provides a detailed analysis of the dissipative phase dynamics and quasiparticle effects following the connection of two BECs, highlighting the transition to semiclassical oscillations.

Findings

Rapid loss of phase coherence after atom exchange

Excitation of quasiparticles within condensates

Transition to damped Josephson plasma oscillations

Abstract

We study the dynamics of the relative phase following the connection of two independently formed Bose-Einstein condensates. Dissipation is assumed to be due to the creation of quasiparticles induced by a fluctuating condensate particle number. The coherence between different values of the phase, which is characteristic of the initial Fock state, is quickly lost after the net exchange of a few atoms has taken place. This process effectively measures the phase and marks the onset of a semiclassical regime in which the system undergoes Bloch oscillations around the initial particle number. These fast oscillations excite quasiparticles within each condensate and the system relaxes at a longer time scale until it displays low-energy, damped Josephson plasma oscillations, eventually coming to a halt when the equilibrium configuration is finally reached.