Impurity effect on the metal-insulator transition in Kondo insulators

Abstract

In this paper we study the effect of transition impurities on the metal-insulator transition in Kondo insulators. We use a two-subband model Hamiltonian in which a strongly correlated electron narrow subband is coupled to a wide conduction-electron subband. In the model, the disorder is treated by using the off-diagonal coherent potential approximation with a simple parametrization of the electron energy hopping. We obtain a criterion for the opening of the hybridization energy gap as a function of impurity concentration. In the particular case of ${\mathrm{CeRh}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x}\mathrm{Sb},$ the insulator-metal transition occurs at critical Pd concentration of 10%, in agreement with experimental data.