Collapse and revival of the monopole mode of a degenerate Bose gas in an isotropic harmonic trap

TL;DR

This paper investigates the monopole mode oscillations of a finite temperature Bose-Einstein condensate in an isotropic harmonic trap, revealing collapse and revival phenomena due to beating between two coupled eigenmodes.

Contribution

It provides the first detailed experimental and theoretical analysis of collapse and revival of monopole oscillations in a finite temperature Bose gas, confirming a two-mode dynamical model.

Findings

Observation of nonexponential collapse and partial revival of oscillations

Identification of beating between in-phase and out-of-phase modes as the cause

Good agreement between experimental data and finite temperature simulations

Abstract

We study the monopole (breathing) mode of a finite temperature Bose-Einstein condensate in an isotropic harmonic trap recently developed by Lobser et al. [Nat.~Phys., \textbf{11}, 1009 (2015)]. We observe a nonexponential collapse of the amplitude of the condensate oscillation followed by a partial revival. This behavior is identified as being due to beating between two eigenmodes of the system, corresponding to in-phase and out-of-phase oscillations of the condensed and noncondensed fractions of the gas. We perform finite temperature simulations of the system dynamics using the Zaremba-Nikuni-Griffin methodology [J.~Low Temp.~Phys., \textbf{116}, 277 (1999)], and find good agreement with the data, thus confirming the two mode description.