Nambu-Goldstone Mode in a Rotating Dilute Bose-Einstein Condensate

TL;DR

This paper investigates the Nambu-Goldstone mode in a rotating 2D dilute Bose-Einstein condensate, revealing its connection to vortex nucleation and how it gains mass as symmetry is restored.

Contribution

It identifies the Nambu-Goldstone mode with the lowest envelope of octupole-mode branches and explains its behavior during vortex nucleation and symmetry restoration.

Findings

Nambu-Goldstone mode linked to vortex nucleation

Mode becomes massive as symmetry is restored

Octupole-mode branches separated by quadrupolar excitations

Abstract

The Nambu-Goldstone mode, associated with vortex nucleation in a harmonically confined, two-dimensional dilute Bose-Einstein condensate, is identified with the lowest-lying envelope of octupole-mode branches, which are separated from each other by the admixture of quadrupolar excitations. As the vortex approaches the center of the condensate and the system's axisymmetry is restored, the Nambu-Goldstone mode becomes massive due to its coupling to higher rotational bands.