Suppressed phonon density and Para conductivity of Cd doped Cu 0.5Tl 0.5Ba 2Ca 3Cu 4− yCd yO 12− δ ( y = 0, 0.25, 0.5, 0.75) superconductors

Abstract

The fluctuation-induced conductivity (FIC) above critical temperature ( T c) was measured in Cd doped (Cu 0.5Tl 0.5)Ba 2Ca 3(Cu 4− y Cd y )O 12− δ ( y = 0, 0.25, 0.5, 0.75) as prepared and oxygen post-annealed superconductors using the Aslamazov–Larkin (AL) and Maki–Thompson (MT) models. From this FIC analysis the coherence length ξ c(0) along the c-axis, inter-plane coupling, dimensionality of fluctuations, the phase relaxation time τ φ and Fermi velocity V F of the carriers were calculated. All of the samples have shown 3D, 2D and 0D fluctuations above T c. T*, the temperature at which the resistivity curve deviates from the linear behavior, is shifted to lower temperatures with increasing Cd concentration. Width of the transition Δ T is shrunked with the enhanced Cd doping. The crossover temperature T o is shifted to lower temperature values with increased Cd contents. Most likely these effects may be arising due to the replacement of Cu atoms by the heavier Cd atoms thereby producing inharmonic oscillations and causes suppression of the density of phonons which in turn suppress T* and Δ T.