Two-fluid model of a Bose-Einstein condensate in the cavity optomechanical regime

TL;DR

This paper models a Bose-Einstein condensate in an optical cavity using a two-fluid approach, revealing complex excitation spectra with potential instabilities, thus advancing understanding of cavity optomechanics with interacting quantum gases.

Contribution

It introduces a two-fluid model for BECs in cavity optomechanics, capturing two-body interactions and excitation spectra, including unstable modes.

Findings

Identification of a gapped upper excitation branch.

Discovery of potential unstable modes in the lower branch.

Enhanced understanding of BEC dynamics in cavity optomechanical systems.

Abstract

We analyze an atomic Bose-Einstein condensate trapped in a high-Q optical cavity driven by a feeble optical field, a situation formally analogous to the central paradigm of cavity optomechanics [Brennecke et al., Science, 322, 235 (2008)]. We account for two-body interactions via a two-fluid model that retains the intuitive appeal of the optomechanical two-mode description. The Bogoliubov excitation spectrum of this system comprises a gapped upper branch and a lower branch that can include an unstable excitation mode.