Theoretical Analysis of the Short Coherence Length Superconductors
K.I. Wysokiński, A. Ciechan and J. Krzyszczak
Institute of Physics and Nanotechnology Centre, M. Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland
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Properties of the short coherence length ξ superconductors are markedly different from those with long ξ. The main difference is connected with their response to impurities. Even the s-wave superconductors have been predicted not to obey the so called Anderson theorem and to show appreciable fluctuations of order parameter. This observation has been recently confirmed in a number of beautiful scanning tunnelling experiments on high temperature cuprate and pnictide superconductors. In this work we study clean two band systems within BCS type approach and impure superconductors within mean field Bogolubov-de Gennes approach. In the weak disorder limit both s-wave and d-wave superconductors only weakly react to impurities. Presence of the Van Hove singularities in the density of states of the two band clean systems strongly increases their superconducting transition temperature if the intra band pair scattering is the only pairing interaction. The effect of impurities on such superconductors does depend on the sign of the inter orbital interaction.
DOI: 10.12693/APhysPolA.118.232
PACS numbers: 71.10.Fd, 74.20.-z, 74.81.-g