Thermal conductivity of bismuth-lead (2223) superconducting cuprates with vanadium/nickel substitutions and evidence for strong electron-phonon coupling

Abstract

Thermal conductivities of a number of vanadium and nickel substituted 2223 (BiPb) superconducting cuprates are reported between 10 and 150K. Substitution of both vanadium and nickel in (BiPb) system influence strongly the magnitude of thermal conductivity (K) of the pellets, both above and below T c. The reduced temperature derivative of the normalised conductivity ( K S K N ) for the reported samples varies between −0.78 and −1.32. Evoking Wiedemann - Franz law the relative magnitude of the carrier and the phonon contributions to total K was estimated. Analysis of K L data using Tewordt-Wolkhausen expression indicates that for all the samples phonon-defect scattering dominates above T c. We further calculate the slope of lattice thermal conductivity at T C and estimate that the slope of carrier thermal conductivity is very large (>8), which indicates strong coupling for some of the carriers in these systems.