THEORY OF THERMAL-CONDUCTIVITY OF THE LATTICE FOR HIGH-TC SUPERCONDUCTORS

The observed peak below Tc in the thermal conductivity κ of YBa2Cu3O7 can be explained by applying the BCS theory for lattice thermal conductivity limited by electron scattering. The contribution of longitudinal acoustic phonons to the electron-phonon coupling constant λ is estimated to lie within the weak coupling range. In addition to phonon-electron scattering we have taken into account scattering of phonons by structural defects like boundaries, point defects, and sheetlike faults. More information about the strength of the phonon-electron scattering and the nature of the gap (weak or strong coupling) could be obtained from measurements of the anisotropy of κ in single crystals.