Inverse Energy Cascade in Forced 2D Quantum Turbulence

TL;DR

This paper demonstrates the occurrence of an inverse energy cascade in forced 2D quantum turbulence modeled by the Gross-Pitaevskii equation, showing energy transfer from small to large scales in a superfluid.

Contribution

It provides the first clear evidence of inverse energy cascade in quantum fluids through numerical simulation of the Gross-Pitaevskii equation with forcing and damping.

Findings

Observation of vortex energy transfer to large scales

Identification of Kolmogorov scaling law in kinetic energy spectrum

Spectral condensation at system size scale

Abstract

We demonstrate an inverse energy cascade in a minimal model of forced 2D quantum vortex turbulence. We simulate the Gross-Pitaevskii equation for a moving superfluid subject to forcing by a stationary grid of obstacle potentials, and damping by a stationary thermal cloud. The forcing injects large amounts of vortex energy into the system at the scale of a few healing lengths. A regime of forcing and damping is identified where vortex energy is efficiently transported to large length scales via an inverse energy cascade associated with the growth of clusters of same-circulation vortices, a Kolmogorov scaling law in the kinetic energy spectrum over a substantial inertial range, and spectral condensation of kinetic energy at the scale of the system size. Our results provide clear evidence that the inverse energy cascade phenomenon, previously observed in a diverse range of classical systems, can also occur in quantum fluids.