Vortex formation and quantum turbulence with rotating paddle potentials in a two-dimensional binary Bose-Einstein condensate

TL;DR

This study explores vortex creation and quantum turbulence in a two-dimensional binary Bose-Einstein condensate driven by rotating paddle potentials, revealing how rotation frequency influences vortex sign, number, and turbulent energy spectra.

Contribution

It introduces a theoretical framework for vortex dynamics in binary BECs with paddle-induced rotation, highlighting the effects of paddle direction and frequency on vortex behavior and turbulence.

Findings

Vortex sign and number depend on paddle rotation frequency.

High rotation speeds lead to vortex-antivortex annihilation and turbulence.

Power-law spectra indicate quantum turbulence at low rotation frequencies.

Abstract

We conduct a theoretical study of the creation and dynamics of vortices in a two-dimensional binary Bose-Einstein condensate with a mass imbalance between the species. To initiate the dynamics, we use one or two rotating paddle potentials in one species, while the other species is influenced only via the interspecies interaction. In both species, the number and the dominant sign of the vortices are determined by the rotation frequency of the paddle potential. Clusters of positive and negative vortices form at a low rotation frequency comparable to that of the trap when using the single paddle potential. In contrast, vortices of the same sign tend to dominate as the rotation frequency of the paddle increases, and the angular momentum reaches a maximum value at a paddle frequency, where the paddle velocity becomes equal to the sound velocity of the condensate. When the rotation frequency is sufficiently high, the rapid annihilation of vortex-antivortex pairs significantly reduces the number of vortices and antivortices in the system. For two paddle potentials rotating in the same direction, the vortex dynamics phenomenon is similar to that of a single paddle. However, when the paddle potentials are rotated in the opposite direction, both positive and negative signed vortices occur at all rotational frequencies. At the low rotation frequencies, the cluster of like-signed vortices produces the $k^{-5/3}$ and $k^{-3}$ power laws in the incompressible kinetic energy spectrum at low and high wavenumbers, respectively, a hallmark of the quantum turbulent flows.