On the optical conductivity of Kondo insulators

The temperature-dependent optical conductivity of a Kondo insulator for different temperatures with impurity doping on the conduction band is studied within the U = infinity Anderson lattice model in the framework of a slave-boson mean-held theory under the coherent potential approximation. The results show that the depletion of the optical conductivity in low-frequency region decreases with increasing of the temperature, and the system exhibits a transition between a low-temperature insulating phase and a high-temperature metallic phase. With increasing of the impurity concentration, the effect of the impurity scattering could result in a nearly temperature-independent gap behavior. The numerical results on the localization of the electron and its variation with temperature are also discussed with the help of optical sum rule.