Ginzburg-Landau expansion and the upper critical field in disordered attractive Hubbard model

Abstract

We present a short review of our studies of disorder influence upon Ginzburg -Landau expansion coefficients in Anderson -Hubbard model with attraction in the framework of the generalized DMFT+Σ approximation. A wide range of attractive potentials U is considered -from weak coupling limit, where superconductivity is described by BCS model, to the limit of very strong coupling, where superconducting transition is related to Bose -Einstein condensation (BEC) of compact Cooper pairs, which are formed at temperatures significantly higher than the temperature of superconducting transition, as well as the wide range of disorders -from weak to strong, when the system is in the vicinity of Anderson transition. For the same range of parameters we study in detail the temperature behavior of orbital and paramagnetic upper critical field Hc2(T ), which demonstrates the anomalies both due to the growth of attractive potential and the effects of strong disordering.