Localized collapse and revival of coherence in an ultracold Bose gas

TL;DR

This paper investigates how dipolar spin waves cause localized collapse and revival of coherence in an ultracold Rb-87 Bose gas, revealing complex dynamics requiring phase-space modeling.

Contribution

It demonstrates the necessity of a phase-space approach to understand localized coherence dynamics induced by spin waves in ultracold gases.

Findings

Localized collapse and revival of Ramsey fringe contrast observed.

Pattern of coherence depends on spin wave excitation strength.

Simple position-space models are insufficient to explain the phenomena.

Abstract

We study the collapse and revival of coherence induced by dipolar spin waves in a trapped gas of Rb-87 atoms. In particular we observe spatially localized collapse and revival of Ramsey fringe contrast and show how the pattern of coherence depends on strength of the spin wave excitation. We find that the spatial character of the coherence dynamics is incompatible with a simple model based only on position-space overlap of wave functions. This phenomenon requires a full phase-space description of the atomic spin using a quantum Boltzmann transport equation, which highlights spin wave-induced coherent spin currents and the ensuing dynamics they drive.