Thermal Properties: Evidence of quasi-normal excitations, D. R. Harshman and J. D. Dow
Previous interpretation of thermal conductivity data of YBa2Cu3O7 in terms of d-wave superconductivity have created the impression that this experiment can only be successfully explained in terms of a d-wave model. Here we show that thermal conductivity data can be (better) explained in terms of s-wave hole-pairing, which also handles some outstanding problems with the d-wave interpretation, namely, muon spectra that are s-wave and specific heat data that that exhibit a zero-field linear-T term. The basic notion is that a high-temperature superconductor such as YBa2Cu3O7 contains both superconducting and normal-like bands. The dominant superconducting bands are associated with BaO, and the CuO2 bands are non-superconducting or only weakly superconducting.
Thermal conductivity divided by temperature (in mW/K2-cm) of YBa2Cu3Oy versus temperature-squared (in K2) for both the insulating (y = 6.0) and superconducting (y = 6.9) compounds.
D. R. Harshman and J. D. Dow, Intern. J. of Mod. Phys. B 19, 147 (2005).