Turbulent relaxation to equilibrium in a two-dimensional quantum vortex gas

Matthew T. Reeves, Kwan Goddard-Lee, Guillaume Gauthier, Oliver R. Stockdale, Hayder Salman, Timothy Edmonds, Xiaoquan Yu, Ashton S. Bradley, Mark Baker, Halina Rubinsztein-Dunlop, Matthew J. Davis, Tyler W. Neely

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Abstract

We experimentally study emergence of microcanonical equilibrium states in the turbulent relaxation dynamics of a two-dimensional chiral vortex gas. Same-sign vortices are injected into a quasi-two-dimensional disk-shaped atomic Bose-Einstein condensate using a range of mechanical stirring protocols. The resulting long-time vortex distributions are found to be in excellent agreement with the mean-field Poisson-Boltzmann equation for the system describing the microcanonical ensemble at fixed energy H and angular momentum M. The equilibrium states are characterized by the corresponding thermodynamic variables of inverse temperature β and rotation frequency ω. We are able to realize equilibria spanning the full phase diagram of the vortex gas, including on-axis states near zero-temperature, infinite temperature, and negative absolute temperatures. At sufficiently high energies the system exhibits a symmetry breaking transition, resulting in an off-axis equilibrium phase at negative absolute temperature that no longer shares the symmetry of the container. We introduce a point vortex model with phenomenological damping and noise that is able to quantitatively reproduce the equilibration dynamics.We experimentally study emergence of microcanonical equilibrium states in the turbulent relaxation dynamics of a two-dimensional chiral vortex gas. Same-sign vortices are injected into a quasi-two-dimensional disk-shaped atomic Bose-Einstein condensate using a range of mechanical stirring protocols. The resulting long-time vortex distributions are found to be in excellent agreement with the mean-field Poisson-Boltzmann equation for the system describing the microcanonical ensemble at fixed energy H and angular momentum M. The equilibrium states are characterized by the corresponding thermodynamic variables of inverse temperature β and rotation frequency ω. We are able to realize equilibria spanning the full phase diagram of the vortex gas, including on-axis states near zero-temperature, infinite temperature, and negative absolute temperatures. At sufficiently high energies the system exhibits a symmetry breaking transition, resulting in an off-axis equilibrium phase at negative absolute temperature that no longer shares the symmetry of the container. We introduce a point vortex model with phenomenological damping and noise that is able to quantitatively reproduce the equilibration dynamics.
Original languageEnglish
Article number011031
JournalPhysical Review X
Volume12
Issue number1
DOIs
Publication statusPublished - 16 Feb 2022

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