2018/01/31 by Shaun P. Johnstone, Andrew J. Groszek, Philip T. Starkey +3
Physics and Astronomy · #cond-mat.quant-gas #physics.flu-dyn
paper · pdf · doi:10.1126/science.aat5793
11 pages, 4 figures, 8 supplementary figures
arxiv created 2018/03/14 · arxiv updated 2019/09/04
Interacting systems driven far from equilibrium tend to evolve to steady states exhibiting large-scale structure and order. In two-dimensional turbulent flow the seemingly random swirling motion of a fluid can evolve towards persistent large-scale vortices. Lars Onsager proposed a model based on statistical mechanics of quantized vortices to explain such behavior. Here we report the first experimental confirmation of Onsager's model of turbulence. We drag a grid barrier through an oblate superfluid Bose--Einstein condensate to generate non-equilibrium distributions of vortices. We observe an inverse energy cascade driven by the evaporative heating of vortices, leading to steady-state configurations characterized by negative temperatures. Our results open a pathway for quantitative studies of emergent structures in interacting quantum systems driven far from equilibrium.