Suppressed phonon density and Para conductivity of Cd doped Cu0.5Tl0.5Ba2Ca3Cu4−yCdyO12−δ (y = 0, 0.25, 0.5, 0.75) superconductors

The fluctuation-induced conductivity (FIC) above critical temperature (Tc) was measured in Cd doped (Cu0.5Tl0.5)Ba2Ca3(Cu4−yCdy)O12−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 ξc(0) along the c-axis, inter-plane coupling, dimensionality of fluctuations, the phase relaxation time τφ and Fermi velocity VF of the carriers were calculated. All of the samples have shown 3D, 2D and 0D fluctuations above Tc. 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 ΔT is shrunked with the enhanced Cd doping. The crossover temperature To 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 ΔT.

► Through FIC analysis, the electron–phonon interactions are studied in (Cu0.5Tl0.5)Ba2Ca3(Cu4−yCdy)O12−δ superconductors. ► LD model, in the mean field region shows the 3D regime and T0 being shifted to lower temperatures with increased Cd content. ► ξc(0), J, VF, τφ, λ and E are not significantly modified with increased Cd-doping. ► Tc(R=0) is shifted to lower temperatures with increased Cd concentration. ► All these conclude that the heavier Cd atoms produce inharmonic oscillations which in turn suppress the phonons population.