Andrew J. Groszek, Matthew J. Davis, Tapio P. Simula
SciPost Phys. 8, 039 (2020) ·
published 12 March 2020
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We numerically model decaying quantum turbulence in two-dimensional
disk-shaped Bose-Einstein condensates, and investigate the effects of finite
temperature on the turbulent dynamics. We prepare initial states with a range
of condensate temperatures, and imprint equal numbers of vortices and
antivortices at randomly chosen positions throughout the fluid. The initial
states are then subjected to unitary time-evolution within the c-field
methodology. For the lowest condensate temperatures, the results of the zero
temperature Gross-Pitaevskii theory are reproduced, whereby vortex evaporative
heating leads to the formation of Onsager vortex clusters characterised by a
negative absolute vortex temperature. At higher condensate temperatures the
dissipative effects due to vortex-phonon interactions tend to drive the vortex
gas towards positive vortex temperatures dominated by the presence of vortex
dipoles. We associate these two behaviours with the system evolving toward an
anomalous non-thermal fixed point, or a Gaussian thermal fixed point,
respectively.
Dr Groszek: "We thank the referee for their..."
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