Reversal of the circulation of a vortex by quantum tunneling in trapped Bose systems

TL;DR

This paper demonstrates that quantum tunneling can cause periodic reversals of vortex circulation in trapped Bose gases, with stability increasing as interactions grow, modeled via a two-site Bose Hubbard analogy.

Contribution

It introduces a quantum dynamical model showing vortex circulation reversal via tunneling, and derives an analytical expression for the oscillation period.

Findings

Vortex circulation can reverse periodically due to quantum tunneling.

Stability of vortices increases with interaction strength and particle number.

The system maps onto a two-site Bose Hubbard model with attractive interactions.

Abstract

We study the quantum dynamics of a model for a vortex in a Bose gas with repulsive interactions in an anisotropic, harmonic trap. By solving the Schr\"odinger equation numerically, we show that the circulation of the vortex can undergo periodic reversals by quantum-mechanical tunneling. With increasing interaction strength or particle number, vortices become increasingly stable, and the period for reversals increases. Tunneling between vortex and antivortex states is shown to be described to a good approximation by a superposition of vortex and antivortex states (a Schr\"odinger cat state), rather than the mean-field state, and we derive an analytical expression for the oscillation period. The problem is shown to be equivalent to that of the two-site Bose Hubbard model with attractive interactions.