title: Emergence of order from turbulence in an isolated planar superfluid.
abstract: We study the relaxation dynamics of an isolated zero temperature quasi-two-dimensional superfluid Bose-Einstein condensate that is imprinted with a spatially random distribution of quantum vortices. Following a period of vortex annihilation the remaining vortices self-organize into two macroscopic coherent "Onsager vortex" clusters that are stable indefinitely--despite the absence of driving or external dissipation in the dynamics. We demonstrate that this occurs due to a novel physical mechanism--the evaporative heating of the vortices--that results in a negative-temperature phase transition in the vortex degrees of freedom. At the end of our simulations the system is trapped in a nonthermal state. Our computational results provide a pathway to observing Onsager vortex states in a superfluid Bose gas.
authors.affiliation: School of Physics, Monash University, Victoria 3800, Australia.
authors.forename: Tapio
authors.initials: T
authors.lastname: Simula
authors.affiliation: School of Mathematics and Physics, University of Queensland, Queensland 4072, Australia.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Davis
authors.affiliation: School of Physics, Monash University, Victoria 3800, Australia.
authors.forename: Kristian
authors.initials: K
authors.lastname: Helmerson