Thermal conductivity and electrical resistivity of the Y- and Er-substituted 1:2:3 superconducting compounds in the vicinity of the transition temperature

Abstract

The thermal conductivity and electrical resistivity of ErBa2Cu3O7−δ and YBa2Cu3O7−δ sintered compounds have been measured to investigate the electron-phonon interaction in the vicinity of Tc in these materials. The thermal conductivity was measured using the transient-plane-source technique. With the electrical-resistivity data and Wiedeman-Franz law, the magnitude of the free-carrier component of the thermal conductivity has been estimated to less than 15% of the measured thermal conductivity. The results in the normal state are interpreted in terms of two models. The first model is the ordinary electron-phonon transport theory applied to high-Tc superconductors, and the second model is the Bardeen-Rickayzen-Tewordt (BRT) theory of the lattice heat conduction in high-Tc superconductors. Both models suggest that the electron-phonon coupling varies from moderately weak to strong coupling depending on characteristic parameters of the considered material such as oxygen content, porosity, Tc value, ΔTc, etc., all of which are directly related to the purity of the investigated samples. Furthermore, using this transient technique a dramatic increase of the thermal conductivity is observed below Tc and the experimental results are in reasonable agreement with the prediction of the generalized BRT theory, adapting a weak coupling with scaled-BCS-gap formalism for the moderately-weak-coupling sample and a strong coupling s-wave-pairing formalism for the strong-coupling sample.

Source-reported materials — not catalogue approval

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