Thermalization, condensate growth, and defect formation in an out-of-equilibrium Bose gas

TL;DR

This study explores how a non-equilibrium Bose gas thermalizes, forms a condensate, and develops defects like gray solitons, combining experiments and simulations to understand out-of-equilibrium dynamics.

Contribution

It provides new insights into the real-time dynamics of Bose gas thermalization, condensate growth, and defect formation using combined experimental and numerical approaches.

Findings

Observation of condensate destruction and growth in a non-equilibrium Bose gas

Detection of gray solitons as defects during evolution

Agreement between experimental results and truncated Wigner simulations

Abstract

We experimentally and numerically investigate thermalization processes of a trapped $^{87}$Rb Bose gas, initially prepared in a non-equilibrium state through partial Bragg diffraction of a Bose-Einstein condensate (BEC). The system evolves in a Gaussian potential, where we observe the destruction of the BEC due to collisions, and subsequent growth of a new condensed fraction in an oscillating reference frame. Furthermore, we occasionally observe the presence of defects, which we identify as gray solitons. We simulate the evolution of our system using the truncated Wigner method and compare the outcomes with our experimental results.