Thermodynamics of two-level atoms interacting with the continuum of electromagnetic field modes
Kazimierz Rza̧żewski, K. Wódkiewicz
We study the thermodynamic properties of two-level atoms interacting with all the modes of the electromagnetic field. We show that the presence of the ${A}^{2}$ term in the interaction Hamiltonian has two important consequences: The divergence difficulties noted previously for the all-mode problem are overcome, so that a formal thermodynamic limit exists; and the phase transition, which occurs in the single-mode case without the ${A}^{2}$ term, is absent.
Physical Review A•May 1, 1976•27 citations