Possible dominance of the Maki–Thompson process in the fluctuation conductivity ofBi-2212 superconducting whiskers

Abstract

We report the measurement of thea-axis fluctuation conductivity in zero field forBi2Sr2CaCu2O8+x microcrystals. A complete geometrical characterization allows us to determine theabsolute value of the excess conductivity and its temperature behaviour with highaccuracy. A careful application of the complete fluctuation theory (Varlamov et al 1999 Adv. Phys. 48 655), which implements a minor correction for the factor and a suitable procedure for disentangling the influence of the different fitparameters, shows that data interpretations excluding the Maki–Thompson (MT) processare either not consistent with the crystal structure or not self-consistent. On the otherhand, a data interpretation including the MT process appears to be both self-consistentand consistent with experimental measurements of the electron dephasing timeτϕ performed in other metallic or semiconducting systems. According to the latterscheme, the anomalous MT term could be a very important contribution to theexcess conductivity throughout the temperature range of interest and thus thes-wave symmetry becomes an important component of the order parameter aboveTc.