  We study the entanglement dynamics in the externally-driven single-mode Dicke
model in the thermodynamic limit, when the field is in resonance with the
atoms. We compute the correlations in the atoms-field ground state by means of
the density operator that represents the pure state of the universe and the
reduced density operator for the atoms, which results from taking the partial
trace over the field coordinates. As a measure of bipartite entanglement, we
calculate the linear entropy, from which we analyze the entanglement dynamics.
In particular, we found a strong relation between the stability of the
dynamical parameters and the reported entanglement.
