The ground-state energy (measured in units of ) of the ground state of the DM with atoms as a function of the scaled coupling parameter . We plot three lines corresponding to different Hamiltonians associated with the DM: the black solid line is related to the energy of , the red dashed line corresponds to , and the blue dotted line corresponds to (in this case, we consider ). We clearly see that, while in the case of the Hamiltonians and the energy of the ground state is unbounded from below in the limit , the energy of the ground state of the total Hamiltonian is bounded as a consequence of the field “self-interacting” term .Reuse & Permissions
Figure 2
The bipartite concurrence between two atoms in the ground state of the DM as a function of the scaled coupling parameter . We use the same notation as in Fig. 1. We can conclude that the interaction with the field mode induces a bipartite entanglement between atoms in the ground state of the Dicke model irrespective of the choice of the Hamiltonian.Reuse & Permissions