title: Inverse energy cascade in forced two-dimensional quantum turbulence.
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.
authors.affiliation: Jack Dodd Centre for Quantum Technology, Department of Physics, University of Otago, Dunedin 9016, New Zealand.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Reeves
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Billam
authors.forename: Brian P
authors.initials: BP
authors.lastname: Anderson
authors.forename: Ashton S
authors.initials: AS
authors.lastname: Bradley