50 research outputs found
Collective modes and the broken symmetry of a rotating attractive Bose gas in an anharmonic trap
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.Comment: 4 pages, 3 eps figures (2 in color) v2: changes in Title, all
figures, in text (especially in Sec III) and in Reference