Fluctuation-Induced Excess Conductivity in R1−x Ca x : 123 Superconductors

Abstract

Fluctuation induced conductivity of Ca substitution at R sites of R1−xCax: 123 superconductors with various x and R is investigated. This work is done by using the reported data of Sedky et al. (Phys. Rev. B 58(18):12495, 1998). The logarithmic plots of Δσ and reduced temperature € reveal three different exponents corresponding to two different crossover temperatures. The first exponent at ln € (−1≥ln €≥−2) and its values are close to 1, for which order parameter dimensionalities (OPD) are two dimensional (2D). The second exponent at ln € (−2≥ln €≥−3.5) and its values are close to 2, for which OPD are neither two dimensional (2D) nor three dimensional (3D). The third exponent at ln € (−3.5≥ln €≥−8) and its values are close to 0.5, for which OPD are three dimensional (3D). The different values of the interlayer coupling are also calculated in the normal and mean field regions, respectively. Our results are discussed in terms of oxygen disorder and system anisotropy produced by Ca substitution in R1−xCax: 123 systems.