Fragmented Many-Body states of definite angular momentum and stability of attractive 3D Condensates

TL;DR

This paper investigates metastable fragmented states in attractive 3D Bose-Einstein Condensates with definite angular momentum, revealing states that persist beyond collapse thresholds and comparing many-body and mean-field descriptions.

Contribution

It identifies and characterizes metastable fragmented excited states with specific angular momentum in attractive BECs, extending understanding beyond the collapsed ground state.

Findings

Existence of metastable fragmented states with overcritical particle numbers.

Spectrum of states with definite angular momentum determined via configuration interaction.

Comparison of many-body and mean-field descriptions of angular momentum states.

Abstract

A three dimensional attractive Bose-Einstein Condensate (BEC) is expected to collapse, when the number of the particles $N$ in the ground state or the interaction strength $\lambda_0$ exceeds a critical value. We study systems of different particle numbers and interaction strength and find that even if the overall ground state is collapsed there is a plethora of fragmented excited states that are still in the metastable region. Utilizing the \emph{configuration interaction} expansion we determine the spectrum of the ground (`yrast') and excited many-body states with definite total angular momentum quantum numbers $0\leqslant L\leqslant N$ and $-L\leqslant M_L\leqslant L$, and we find and examine states that survive the collapse. This opens up the possibility of realizing a metastable system with overcritical numbers of bosons in a ground state with angular momentum $L\neq0$. The multi-orbital mean-field theory predictions about the existence of fragmented metastable states with overcritical numbers of bosons are verified and elucidated at the many-body level. The descriptions of the total angular momentum within the mean-field and the many-body approaches are compared.