Decaying superfluid turbulence near an anomalous non-thermal fixed point

Abstract:

Anomalously slow coarsening in a dilute two-dimensional (2d) superfluid — associated with a non-thermal fixed point in the closed system’s universal dynamics and driven by three-vortex collisions which initiate vortex-pair annihilations — is found to exhibit spatial scaling characteristics of Kraichnan-Kolmogorov turbulence. During a universal interval, when the characteristic length scale related to the inter-defect distance grows as , with , moments of the superfluid velocity circulation around an area of extent scale as predicted by classical turbulence theory, . Intermittency corrections seen for higher values of are found to be consistent with values measured for fully developed, classical turbulence. Hence, we link the decaying quantum turbulence cascade in a closed superfluid to universal dynamics close to a non-thermal fixed point. The decay exponent clearly deviates from values known for classical systems.