Vortex nucleation in mesoscopic Bose superfluid and breaking of the parity symmetry

TL;DR

This paper investigates vortex nucleation and parity symmetry breaking in a mesoscopic 2D Bose superfluid under rotation, revealing a transition from mean-field to strongly correlated entangled states near the critical rotation frequency.

Contribution

It demonstrates the occurrence of discrete parity symmetry breaking and the emergence of a strongly correlated entangled many-body state in a rotating mesoscopic Bose superfluid.

Findings

Parity symmetry is broken at the critical rotation frequency.

The many-body state becomes a maximally entangled two-mode state.

Dynamical instability occurs in the mean-field solutions near the critical point.

Abstract

We analyze vortex nucleation in mezoscopic 2D Bose superfluid in a rotating trap. We explicitly include a weakly anisotropic stirring potential, breaking thus explicitly the axial symmetry. As the rotation frequency passes the critical value $\Omega_c$ the system undergoes an extra symmetry change/breaking. Well below $\Omega_c$ the ground state is properly described by the mean field theory with an even condensate wave function. Well above $\Omega_c$ the MF solution works also well, but the order parameter becomes odd. This phenomenon involves therefore a discrete parity symmetry breaking. In the critical region the MF solutions exhibit dynamical instability. The true many body state is a strongly correlated entangled state involving two macroscopically occupied modes (eigenstates of the single particle density operator). We characterize this state in various aspects: i) the eligibility for adiabatic evolution; ii) its analytical approximation given by the maximally entangled combination of two single modes; and finally iii) its appearance in particle detection measurements.