The role of Coulomb correlations in LaFeAsO is studied by generalizing exact diagonalization dynamical mean field theory to five orbitals [1]. For rotationally invariant Hund coupling a spin freezing transition from a paramagnetic Fermi-liquid to a non-Fermi-liquid metallic phase is found at U = 3 eV, J = 0.75 eV. For Ising exchange, this transition occurs at about U = 2 eV.

The correlation-induced scattering rate as a function of doping relative to half-filling, delta=n/5-1, where n=6 for the undoped material, is shown to be similar to the one in the two-dimensional single-band Hubbard model.

In this scenario, the parent Mott insulator of LaFeAsO is the half-filled n=5 limit, while the undoped n=6 material corresponds to the critical doping region delta_c ~ 0.2 in the cuprates, on the verge between the Fermi-liquid phase of the overdoped region and the non-Fermi-liquid pseudogap phase in the underdoped region.

[1] H. Ishida and A. Liebsch, Phys. Rev. B 81, xxx (2010).