Superconductivity in impurity bands
Agafonov A.I., Manykin E.A.
We present a theory of superconductivity in doped insulators. In the magnetic metal state of the compound we obtain the self-consistency equations for the superconducting state in the spin-dependent impurity bands of both extended and localized states in the initial insulator gap. A BCS-type triplet pairing field is considered. We show that the superconducting gap in which single-electron extended states do not exist is overlapped by the distribution of the localized states. The formation of a latent superconducting gap is discussed in connection with the unusual properties of high-Tc compounds. PACS: 71.27.+a, 71.30.-fh, 74.20.Mn, 74.72.-h