Speaker
Description
Our work focuses on decaying quantum turbulence in the vicinity of an anomalous non-thermal fixed point (NTFP) characterized by slow, subdiffusive coarsening of a length scale. The NTFP is approached in the temporal evolution of a quasi-2d dilute Bose gas starting from variously sampled initial vortex configurations. The universal dynamics is accompanied by the build-up of an inverse energy cascade following the Kraichnan-Kolmogorov $k^{-5/3}$ power law in the incompressible energy spectrum. By studying higher moments of the velocity circulation, we observe spatial intermittency when the system is close to the anomalous non-thermal fixed point. Due to the irreversible conversion of incompressible (vortices) into compressible energy (sound) the observed universal dynamics can be understood in the context of decaying, compressible turbulence. The universal characteristics is seen in a similar fashion in systems with contact as well as long-range dipolar interactions. While the spatial characteristics resemble that of classical Kraichnan-Kolmogorov turbulence, the subdiffusive universal temporal scaling exponent $\beta\approx1/5$, which defines the algebraic coarsening of the vortex pattern is found to be distinctly different from results known for classical fluids.