Pairing Correlations around Negative-U Centre in the Two-Band Model

Abstract

The electron energy spectrum of many superconducting materials is characterised by the presence of few bands at the Fermi level. In some cases the superconducting properties seem to be dominated by single band but in others the many-band approach is essential ingredient of their description. In this paper we shall study the properties of superconducting impurity placed in a non-superconducting medium. We are interested in the evolution of superconducting correlations within non-superconducting 1-or 2-dimensional system, their dependence on the distance from impurity and changes induced by the presence of the second band and interband scattering. We use real space description of the material and Bogolyubov-de Gennes approach to superconductivity.

Inhomogeneities in superconductors: two component and two band scenarios

“…are expressed in terms of eigenvectors u kλ ( r i ) and v kλ ( r i ) and eigenvalues E k of BdG equations [15] and evaluated self-consistently. Here f k = (exp(βE k )+1) −1 is the Fermi -Dirac distribution function and β = 1/k B T .…”

Theoretical Analysis of the Short Coherence Length Superconductors

“…Contrary to the k-space based approaches we do not average over disorder and study the properties of the system with a given configuration of impurities. In the previous studies [20] we have applied similar method to find pairing correlations around two-orbital impurity in a metallic host.…”