Ferromagnetic transition temperature of a two-band model for diluted magnetic semiconductors

Within dynamical-mean field theory we investigate the ferromagnetic transition temperature ($T_{c}$) of a two-band model for diluted magnetic semiconductors in a large range of coupling constants, hopping parameters, and carrier densities [1]. We reveal that $T_{c}$ is optimized at all fillings when both impurity bands fully overlap in the same energy interval, namely when the exchange couplings and bandwidths are equal. The optimal $T_{c}$ is found to be about twice larger than the maximal value obtained in the one-band model. Within a one-band model we also discuss the influence of the Coulomb attractive potential by acceptors on the critical ferromagnetic temperature [2]. \newline [1]. F. Popescu, Y. Yildirim, G. Alvarez, A. Moreo, and E. Dagotto, Phys. Rev. B, 73 (2006), 075206. \newline [2]. F. Popescu, C. Sen, E. Dagotto, and A. Moreo, in preparation.