Many-body approach to low-lying collective excitations in a BEC approaching collapse

TL;DR

This paper develops a many-body theoretical approach to analyze low-lying collective excitations in a Bose-Einstein condensate, revealing significant deviations from traditional models near collapse conditions due to two-body correlations.

Contribution

It introduces an approximate many-body method that incorporates two-body correlations to accurately predict collective modes in a BEC near collapse, surpassing the Gross-Pitaevskii and hydrodynamic models.

Findings

Significant differences from Gross-Pitaevskii estimates near collapse.

Large deviations from hydrodynamic model for certain modes.

Two-body correlations and finite-range interactions are crucial.

Abstract

An approximate many-body theory incorporating two-body correlations has been employed to calculate low-lying collective multipole frequencies in a Bose-Einstein condensate containing $A$ bosons, for different values of the interaction parameter $\lambda=\frac{Aa_{s}}{a_{ho}}$. Significant difference from the variational estimate of the Gross-Pitaevskii equation has been found near the collapse region. This is attributed to two-body correlations and finite range attraction of the realistic interatomic interaction. A large deviation from the hydrodynamic model is also seen for the second monopole breathing mode and the quadrupole mode for large positive $\lambda$.