Fluctuation Induced Conductivity in Hg-Doped (Cu0.5Tl0.5−xHgx)Ba2Ca3Cu4O12−δ Superconductor

The fluctuation induced conductivity (FIC) analysis on resistivity data of the Hg-doped (Cu0.5Tl0.5−x Hg x )Ba2Ca3Cu4O12−δ (x=0, 0.15, 0.25, 0.35) superconductor has been carried out in the light of the Aslamazov–Larken (AL) theory. The superconducting properties have been improved with Hg-doping (up to x=0.25) at Tl sites in the Cu0.5Tl0.5Ba2O4−y charge reservoir layer. These samples are also post-annealed in oxygen to improve intergrain connectivity and to optimize the carriers’ density in CuO2 planes. The results of FIC analysis have shown three-dimensional (3D) and two-dimensional (2D) fluctuations in the order parameters. It has been observed that there is an increase in the cross-over temperature (T o) as well as in zero resistivity critical temperature {T c(0)} with Hg-doping. These properties have been further improved after post-annealing in oxygen, which may be due to improved inter-grain coupling and optimization of mobile carriers in CuO2 planes. A direct correlation between T o, T c(0) as well as zero temperature coherence length ξ c(0) has been observed.