  We consider the entanglement properties of the quantum phase transition in
the single-mode superradiance model, involving the interaction of a boson mode
and an ensemble of atoms. For infinite system size, the atom-field entanglement
of formation diverges logarithmically with the correlation length exponent.
Using a continuous variable representation, we compare this to the divergence
of the entropy in conformal field theories, and derive an exact expression for
the scaled concurrence and the cusp-like non-analyticity of the momentum
squeezing.
