In this work, we investigate the superradiant phase transition in a two-atom Rabi model with dipole-dipole interactions, which occurs at the finite-frequency limit due to spontaneous breaking of the $Z_2$ symmetry. Upon analyzing the energy spectrum, it is observed that these dipole-dipole interactions induce a shift of the phase-transition point. Interestingly, we find that, as the strength of the light-atom interaction increases, the atoms entangled by dipole-dipole interactions tend to be decoupled. Moreover, such dipole-dipole interactions enable the Rabi model to undergo the superradiant phase transition in the presence of the $A^2$ term. Our results implement the superradiant phase transition beyond the no-go theorem in the two-atom Rabi model and provide a feasible way to explore multi-atom Rabi models with more complex interactions.

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• Cavity quantum electrodynamics
• Phase transitions
• Superradiance & subradiance
• Rabi model