The Two-Photon Jaynes-Cummings Model: A Coherent State Approach
Flávio Cordeiro, Constança Providência, Seiya Nishiyama
Abstract
It is shown, by conventional mean-field technics, that su(2)⊗su(1, 1) coherent states are a good choice for describing the two-photon Jaynes-Cummings model in the sense that results based on mean-field methods for those states are in good agreement with exact results. We also find that this agreement is much improved if the constant of motion of the model is implemented exactly instead of being implemented only in the average. This is done by projecting the su(2) ⊗ su(1, 1) coherent states onto the physical subspaces. It is seen that the Hamiltonian of the model is unbounded from below, i.e., it lacks a ground-state. We also present and study a stabilized version of the model such that the relevant physical features are preserved. Along the article, special attention is given to the description of the super-radiant phase transition exhibited by the model.