Collective modes and the broken symmetry of a rotating attractive Bose gas in an anharmonic trap

TL;DR

This paper investigates the rotational behavior and collective excitations of an attractive Bose gas in an anharmonic trap, revealing how interactions influence vortex stability and symmetry-breaking modes.

Contribution

It provides a detailed analysis of low-lying excitations and symmetry-breaking phenomena in rotating attractive Bose gases within anharmonic potentials.

Findings

Vortex excitation spectrum becomes negative with stronger interactions.

Broken rotational symmetry leads to an extra zero-energy mode.

Coupling between center of mass and relative motions observed.

Abstract

We study the rotational properties of an attractively interacting Bose gas in a quadratic + quartic potential. The low-lying modes of both rotational ground state configurations, namely the vortex and the center of mass rotating states, are solved. The vortex excitation spectrum is positive for weak interactions but the lowest modes decrease rapidly to negative values when the interactions become stronger. The broken rotational symmetry involved in the center of mass rotating state induces the appearance of an extra zero-energy mode in the Bogoliubov spectrum. The excitations of the center of mass rotational state also demonstrate the coupling between the center of mass and relative motions.