Trapped Bose-Einstein Condensates with Attractive s-wave Interaction
arXiv:1909.02432
Abstract
Within the framework of the Gaussian-state theory, we show that the quantum many-body ground state of a trapped condensate with weakly attractive interaction is a single-mode squeezed vacuum state, as oppose to the coherent state under repulsive interaction. The spatial mode of the squeezed-state condensates satisfies a Gross-Pitaevskii like equation in which the interaction strength is augmented by a factor due to the large particle fluctuation of the squeezed state. We also study the collective excitations of the condensates by the tangential space projection, which leads to new two-particle excitations and confirms the phase transition from coherent-state to squeezed-state condensates. Our investigation clarifies the quantum states of the attractive condensates and will shed new light on research of the droplet phases in dipolar and multicomponent condensates.
arXiv comment5 pages 2 figures
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