Kondo lattice model at half-filling

In this paper, we have studied the single- and two-channel Kondo lattice model consisting of localized spins interacting anti-ferromagnetically with itinerant electrons. We have employed the dynamical mean field theory and have used the exact diagonalization method in our impurity solver. This method allowed us to access low temperatures and large values of exchange couplings. Our results for the single- channel case confirm and extend the recent investigations. In the two-channel case, at absolute zero temperature for half-filling and for the exchange couplings J/t > 0.8, we have found a spontaneous symmetry breaking quantum phase transition, with one band showing a metallic behavior and the other showing an insulating behavior. Finally, our calculations for the two-channel case show the existence of an anti-ferromagnetic phase for all coupling strengths of physical interest.