SUPERCONDUCTIVITY IN IMPURITY BANDS

We present a theory of superconductivity in doped insulators. In the m agnetic metal state of the compound we obtain the self-consistency equ ations for the superconducting state in the spin-dependent impurity ba nds of both extended and localized states in the initial insulator gap . A BCS-type triplet pairing field is considered. We show that the sup erconducting gap in which single-electron extended states do not exist is overlapped by the distribution of the localized states. The format ion of a latent superconducting gap is discussed in connection with th e unusual properties of high-T-c compounds. (C) 1997 American Institut e of Physics.