Superconductivity and Fluctuation-Induced Conductivity (FIC) Analysis of (Cu0.5Tl0.5−x M x )Ba2Ca2Cu3O10−δ

Abstract

Superconductivity has been improved by partial substitution of slightly higher electronegative (M=Bi, Hg) elements at Tl sites in (Cu0.5Tl0.5−xMx)Ba2O4−δ (x=0,0.25) charge reservoir layer of (Cu0.5Tl0.5−xMx)Ba2Ca2Cu3O10−δ superconductor. These samples were characterized by X-ray diffractometry, dc-resistivity, ac-susceptibility, FTIR absorption spectroscopy, and fluctuation-induced conductivity (FIC) analysis. The FIC analysis has been carried out in the light of Aslamasov–Larkin (AL) theory on the resistivity versus temperature curves of (Cu0.5Tl0.5−xMx)Ba2Ca2Cu3O10−δ superconductor. The microscopic parameters such as cross-over temperature (To), zero-temperature coherence length ξc(0), inter-layer coupling (J), and critical exponents (λ2D and λ3D) have been determined from FIC analysis of these samples and tried to correlate them to the superconductivity order parameters. A direct correlation between the cross-over temperatures (To) and zero resistivity critical temperature {Tc(R=0)} and carrier concentration in these samples has been observed. The improvement in Tc(R=0) and the shift of 3D AL region to higher temperature values with the doping of Bi and Hg have also been observed.