Nonlinear atom-photon-interaction-induced population inversion and inverted quantum phase transition of Bose-Einstein condensate in an optical cavity

Xiuqin Zhao, Ni Liu, and J.-Q. Liang
Phys. Rev. A 90, 023622 – Published 15 August 2014

Abstract

In this paper we explore the rich structure of macroscopic many-particle quantum states for a Bose-Einstein condensate in an optical cavity with a tunable nonlinear atom-photon interaction [K. Baumann et al., Nature (London) 464, 1301 (2010)]. Population inversion, bistable normal phases, and the coexistence of normal-superradiant phases are revealed by adjusting the experimentally realizable interaction strength and pump-laser frequency. For the negative (effective) cavity frequency we observe, remarkably, an inverted quantum phase transition (QPT) from the superradiant to the normal phases with an increase in atom-field coupling, which is just opposite the QPT in the normal Dicke model. Bistable macroscopic states are derived analytically in terms of the spin-coherent-state variational method by taking into account both normal and inverted pseudospin states.

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  • Received 5 May 2014

DOI:https://doi.org/10.1103/PhysRevA.90.023622

©2014 American Physical Society

Authors & Affiliations

Xiuqin Zhao1,2, Ni Liu3, and J.-Q. Liang1,*

  • 1Institute of Theoretical Physics, Shanxi University, Taiyuan, Shanxi 030006, China
  • 2Department of Physics, Taiyuan Normal University, Taiyuan, Shanxi 030001, China
  • 3School of Physics and Electronic Engineering, Shanxi University, Taiyuan, Shanxi 030006, China

  • *jqliang@sxu.edu.cn

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Vol. 90, Iss. 2 — August 2014

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