Influence of a distribution of critical temperatures on the paraconductivity and the fluctuation magnetoconductivity in high-temperature superconductors

Abstract

A phenomenological model which considers the effect of a non-uniform critical temperature on the various thermodynamic fluctuation contributions to the paraconductivity and to the magnetoconductivity is presented. Assuming a Gaussian distribution of critical temperatures, only a small change of the paraconductivity, but a significant enhancement of the fluctuation magnetoconductivity was found in the vicinity of T c. The shape of the magnetic field dependence of the fluctuation magnetoresistance is substantially changed, in particular the quadratic region of the low-field limit is shifted to smaller magnetic fields. The present results are compared with recent experimental findings in thin films of (Bi, Pb) 2Sr 2Ca 2Cu 2O x and consequences for an analysis of the dimensional crossover in the layered superconductor model are discussed.