Is there a spontaneous breaking of the parity symmetry of the Jaynes - Cummings model without the rotating-wave approximation?
Chi‐Fai Lo, K L Liu, K.M. Ng, Piu-Hung Yuen · Quantum and Semiclassical Optics Journal of the European Optical Society Part B · 1998
Recently, Bishop and co-workers (1996 Phys. Rev. A 54 R4657) applied the coupled-cluster method to study the ground state of the Jaynes - Cummings model without the rotating-wave approximation and reported strong evidence for a second-order quantum phase transition which was believed to be caused by spontaneous breaking of the parity symmetry of the system. In the present work we have re-investigated this conjecture via examining the nature of the exact (numerical) ground state of the system. Our analysis has indicated that the ground state has definite positive parity and there is no spontaneous breaking of the parity symmetry of the system.