Role of thermal friction in relaxation of turbulent Bose-Einstein condensates

TL;DR

This paper analyzes how thermal friction influences the relaxation of turbulent Bose-Einstein condensates, showing a linear relationship between vortex decay rate and thermal friction coefficient through experiments and simulations.

Contribution

It provides a comparative analysis of experimental data and numerical simulations, demonstrating the linear dependence of vortex decay rate on thermal friction in turbulent BECs.

Findings

Vortex decay rate is nearly linearly proportional to thermal friction coefficient.

Numerical simulations confirm the linear relationship between decay rate and thermal friction.

Strong thermal friction prevents the formation of vortex-clustered states in decaying turbulence.

Abstract

In recent experiments, the relaxation dynamics of highly oblate, turbulent Bose-Einstein condensates (BECs) was investigated by measuring the vortex decay rates in various sample conditions [Phys. Rev. A $\bf 90$, 063627 (2014)] and, separately, the thermal friction coefficient $\alpha$ for vortex motion was measured from the long-time evolution of a corotating vortex pair in a BEC [Phys. Rev. A $\bf 92$, 051601(R) (2015)]. We present a comparative analysis of the experimental results, and find that the vortex decay rate $\Gamma$ is almost linearly proportional to $\alpha$. We perform numerical simulations of the time evolution of a turbulent BEC using a point-vortex model equipped with longitudinal friction and vortex-antivortex pair annihilation, and observe that the linear dependence of $\Gamma$ on $\alpha$ is quantitatively accounted for in the dissipative point-vortex model. The numerical simulations reveal that thermal friction in the experiment was too strong to allow for the emergence of a vortex-clustered state out of decaying turbulence.