Phase Transition and Superfluid of Photons and Photon Pairs in a Two-Dimensional Optical Microcavity

We analyze the ground-state properties and the excitation spectrum of Bose-Einstein condensates of photons and PPs in a two-dimensional optical microcavity. First, using the variational method, we discuss the ground-state phase transition of the two-component system. We also investigate the energy gap between the ground state and the first excited state. Moreover, by investigating the excitation spectrum, we also illustrate how the superfluid behavior of photons and PPs can be associated with the phase transition of the system.