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

We report the measurement of the a-axis fluctuation conductivity in zero field for Bi2Sr2CaCu2O8+x microcrystals. A complete geometrical characterization allows us to determine the absolute value of the excess conductivity and its temperature behaviour with high accuracy. A careful application of the complete fluctuation theory (Varlamov et al 1999 Adv. Phys. 48 655), which implements a minor correction for the k-tilde factor and a suitable procedure for disentangling the influence of the different fit parameters, shows that data interpretations excluding the Maki-Thompson (MT) process are either not consistent with the crystal structure or not self-consistent. On the other hand, a data interpretation including the MT process appears to be both self-consistent and consistent with experimental measurements of the electron dephasing time τφ performed in other metallic or semiconducting systems. According to the latter scheme, the anomalous MT term could be a very important contribution to the excess conductivity throughout the temperature range of interest and thus the s-wave symmetry becomes an important component of the order parameter above Tc