Light-shift-induced quantum phase transitions of a Bose-Einstein condensate in the optical cavities

TL;DR

This paper investigates the complex ground-state phase diagram of a Bose-Einstein condensate in an optical cavity, revealing new quantum phase transitions induced by light shifts and nonlinear atom-photon interactions, including coexistence points.

Contribution

It introduces a detailed analysis of phase diagrams and predicts novel quantum phase transitions driven by detuning, expanding understanding of atom-photon coupled systems.

Findings

Identification of two new quantum phase transitions in blue detuning.

Prediction of three-phase coexistence points.

Clarification that certain coexistence regions are not present in the ground state.

Abstract

In this paper we reveal the rich ground-state properties induced by the strong nonlinear atom-photon interaction, which has been found in the recent experiment about a Bose-Einstein condensate coupling with a high-finesse cavity [Nature (London) 464, 1301 (2010)]. Two detuning-dependent phase diagrams are revealed by investigating the experimentally-measurable atomic population. In particular, two new quantum phase transitions from the superradiant phase or the normal phase to a dynamically-unstable phase are predicted in the blue detuning, and moreover, the three-phase coexistence points are found. It is also demonstrated that these predicted quantum phase transitions are the intrinsic transitions governed only by the second-order derivative of the ground-state energy. Finally, we also point out that the region involving coexistence of the superradiant phase and the normal phase predicted before can not happen in the ground state.