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

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 $90$, 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 $92$, 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.

7 pages, 5 figures

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• Turbulent relaxation to equilibrium in a two-dimensional quantum vortex gas
• Relative dynamics of quantum vortices and massive cores in binary BECs
• Mutual friction and diffusion of two-dimensional quantum vortices
• Sound emission and annihilations in a programmable quantum vortex collider
• Measuring mutual friction in superfluids: the role of initial vortex configuration fluctuations
• Annihilation and recurrence of vortex-antivortex pairs in two-component Bose-Einstein condensates
• Mutual friction and vortex Hall angle in a strongly interacting Fermi superfluid