Determination of the dimensionality of order parameter fluctuations in polycrystalline Bi2Sr2CaCu2O8+δ

Abstract

Fluctuation conductivity, Δσ, is the term contributed by thermodynamic fluctuations to the normal dc conductivity. It causes a metal to deviate from the normal behavior of linear dependence between resistance and temperature. Previous studies on high-T_c oxide superconductors have recognized that the resistive transition displays rounding features that strongly suggest the occurrence of enhanced fluctuations in the normal state. The enhanced fluctuations being attributed to the short coherence length and high critical temperatures intrinsic to this particular type of superconductors.
The above conditions are suitable for fluctuation studies and as such, are utilized to probe the dimensionality of the order parameter fluctuations of different high-temperature superconductor materials. The determination of the dimensionality of the order parameter fluctuations and fluctuation studies in general are of importance in the development of a more comprehensive superconducting theory that requires the knowledge of the conductivity mechanism involved in these high-T_c superconductors.
This paper presents the measurement of the temperature dependence of the resistivity of polycrystalline Bi-2212 samples. The results are analyzed within the Azlamasov-Larkin (AL) model of which a dominating 3D behavior is found for both samples.