Theory of dirty type-II superconductors

Abstract

A theory of dirty type-II superconductors is proposed, which describes the behavior of the vortex state not only in the high-field region but also in the intermediate-field region. We construct the theory by taking into account the self-energy corrections to the electron Green function due to the presence of the spatially varying order parameter by the method similar to the one used previously by Brandt, Pesch, and Tewordt in their study of pure type-II superconductors. Making use of this Green function, we calculate thermodynamic as well as dynamic properties of dirty type-II superconductors, which describe quite well the observed behavior in the wider range of the vortex state. In particular, we obtain a sharp decrease of the flux-flow resistivity immediately below the upper critical field, while thermodynamic quantities vary smoothly in the same region. This accounts for the discrepancy so far found between the theory and the experiment for the flux-flow conductivity in the vortex state.