We study the asymmetric Hubbard model at half-filling as a generic model to describe the physics of two species of repulsively interacting fermionic cold atoms in optical lattices. We use Dynamical Mean Field Theory to obtain the paramagnetic phase diagram of the model as function of temperature, interaction strength and hopping asymmetry. A Mott transition with a region of two coexistent solutions is found for all nonzero values of the hopping asymmetry. At low temperatures the metallic phase is a heavy Fermi-liquid, qualitatively analogous to the Fermi liquid state of the symmetric Hubbard model. Above a coherence temperature, an orbital-selective crossover takes place, wherein one fermionic species effectively localizes, and the resulting bad metallic state resembles the non-Fermi liquid state of the Falicov-Kimball model. We compute observables relevant to cold atom systems such as the double occupation, the specific heat and entropy and characterize their behavior in the different phases.PACS numbers: 67.85. Lm, 71.30.+h, 71.10.Fd Quantum degenerate fermions can now be loaded onto optical lattices to recreate model hamiltonians with easily tunable physical parameters [1]. Two fermionic atomic species are minimally required to create a spin-1/2 model, where each type of atom is associated to a different projection of the spin. This can be achieved by either loading the optical lattice with atoms with two different hyperfine spin states or by two different atom species [1][2][3][4][5]. Remarkable aspects of the cold atom systems include the variety of lattice-types that can be realized, and the large range of interaction strengths that can be accessed, that may be up to several times the fermion bandwidth [6]. A lot of recent work has focused on the fermionic Hubbard model in 3D optical lattices, which is the paradigm of a strongly correlated fermionic system. For instance, a BCS-BEC crossover was observed in the attractive case using 6 Li atoms [7,8], and also a Mott insulating state was reported in the repulsive case at half-filling using 40 K atoms [9,10]. Although the exact realization of the Hubbard model may be achieved in cold atom systems, the generic situation, involving two different fermionic atomic species, will not exactly fulfill the requirement of spin symmetry. Thus, the model typically realized in an optical lattice would be an Asymmetric Hubbard model (AHM), which interpolates between the Hubbard model and the spinless Falicov-Kimball model (FKM), with or without population imbalance. This model, in the case of attractive interactions, has been considered in recent theoretical investigations that focused on the possibility of superconducting phases [2,4]. The study of the AHM with repulsive interactions is therefore relevant and may provide needed guidance for current experimental investigations.In this paper, we focus on the interesting case of the half filled AHM with no population imbalance and the associated paramagnetic Mott metal-insulator transition. For simplicity, we neglect the h...

In a system where selective Mott localization is realized, some electrons show a gap to charge excitations while others do not. A hybridization between these two kind of electrons will lead to a smoothening of this sharp difference and can even bring the system back to a complete delocalization. We show here that there is a large region of parameters at finite hybridization where the selective localization persists and the system shows a partial filling of the selective gap with incoherent states, giving rise to a pseudogap. This result is illustrated here in a two orbital Hubbard model with Hund's coupling, but is based on quite general assumptions and should hold for a larger class of systems, and possibly be a paradigm for the pseudogap mechanism in cuprates.