Evolution of largescale flow from turbulence in a twodimensional superfluid
Abstract
Nonequilibrium interacting systems can evolve to exhibit largescale structure and order. In twodimensional turbulent flow, the seemingly random swirling motion of a fluid can evolve toward persistent largescale vortices. To explain such behavior, Lars Onsager proposed a statistical hydrodynamic model based on quantized vortices. Here, we report on the experimental confirmation of Onsager’s model. We dragged a grid barrier through an oblate superfluid Bose─Einstein condensate to generate nonequilibrium distributions of vortices. We observed signatures of an inverse energy cascade driven by the evaporative heating of vortices, leading to steadystate configurations characterized by negative absolute temperatures. Our results open a pathway for quantitative studies of emergent structures in interacting quantum systems driven far from equilibrium.
 Publication:

Science
 Pub Date:
 June 2019
 DOI:
 10.1126/science.aat5793
 arXiv:
 arXiv:1801.06952
 Bibcode:
 2019Sci...364.1267J
 Keywords:

 PHYSICS;
 Condensed Matter  Quantum Gases;
 Physics  Fluid Dynamics
 EPrint:
 11 pages, 4 figures, 8 supplementary figures