Quantum phase transitions of a two-atom Rabi model with dipole-dipole interactions

Hongbo Liang, Wen-Nian Liu, Wen-Bo Li

Yan Zhang, Wen-Bo Li, Bin-Bin Mao +1 more

Lei Tan, Yuqing Zhang, Wu‐Ming Liu

We investigate the quantum phase transitions for two weakly coupled atom-cavity sites. The interatomic dipole-dipole interaction is considered. Our numerical results show that the dipole-dipole interaction is a crucial parameter for the quantum phase transition. For small atom-cavity detuning, the ``superfluid'' becomes more and more obvious with the increase of the dipole-dipole interaction. In addition, the strong dipole-dipole interaction can lead the atomic excitation to be suppressed completely, and only the photonic excitation exists for the ground states. When the atom-cavity detuning is comparable with the dipole-dipole interaction, the dipole-dipole interaction enlarges the positive detunings, which is in favor of exhibiting superfluid photonic states. While for the negative detuning, the dipole-dipole interaction will reduce it, and contribute to the formation of the polaritonic insulator states. The cases for extended models have also been briefly analyzed. We also discuss how to find these novel phenomena in future experiments.

S. A. Chilingaryan

M. Aparicio Alcalde, A. H. Cardenas, Nami Fux Svaiter +1 more

The full Dicke model is composed of a single bosonic mode and an ensemble of $N$ identical two-level atoms. In the model, the coupling between the bosonic mode and the atoms generates resonant and nonresonant processes. We also consider a dipole-dipole interaction between the atoms, which is able to generate entangled states in the atomic system. By assuming thermal equilibrium with a reservoir at temperature ${\ensuremath{\beta}}^{\ensuremath{-}1}$, the transition from fluorescent to superradiant phase and the quantum phase transition are investigated. It is shown that the critical behavior of the full Dicke model is not modified by the introduction of the dipole-dipole interaction.

Amit Dutta, G. Aeppli, Bikas K. Chakrabarti +3 more