Thermodynamic properties of the Dicke model in the strong-coupling regime

We discuss the problem of a N two-level systems interacting with a single radiation mode in the strong-coupling regime. The thermodynamic properties of Dicke model are analyzed developing a perturbative expansion of the partition function in the high-temperature limit and we use this method to investigate the connections between the Dicke and the collective one-dimensional Ising modelComment: 7 pages, accepted for publication in EPJ

Scaling behavior in the adiabatic Dicke Model

We analyze the quantum phase transition for a set of $N$-two level systems interacting with a bosonic mode in the adiabatic regime. Through the Born-Oppenheimer approximation, we obtain the finite-size scaling expansion for many physical observables and, in particular, for the entanglement content of the system.Comment: 4 pages, 3 figure