Superconducting fluctuation probed by in-plane and out-of-plane conductivities in Tl₂Ba₂CaCuO_8+y single crystals

Extensive measurements of the in-plane and the out-of-plane zero field resistivities [ρ_ab(T.0),ρ_c(T,0)] and the magnetoresistivities [ρ_ab(T,H), ρ_c(T,H)] of high-quality Tl₂Ba₂CaCu₂O_8+y single crystals were carried out. The obtained zero field fluctuation conductivities [Δσ_ab(T,0), Δσ_c-(T,0)] and fluctuation-induced magnetoconductivities [Δσ_ab(T,H) and Δσ_c(T,H)] were analyzed based on the theory of thermal fluctuations of the superconducting order parameters, originated from fluctuations of the quasiparticle density of states as well as the Aslamazov-Lakin and Maki-Thompson contributions. We observed that Δσ_ab(T,H) and the sign change in Δσ_c(T,H) near T_c could be described adequately only if the density of states contribution was included. The important physical parameters, such as the coherence length (ε), the in-plane scattering time (τ), and the hopping integral (J), obtained during these analyses are compared with the corresponding parameters for other high-T_c materials.