Effect of Magnetic Field on Thermal Conductivity of YBa2Cu3O(7-Delta) SingleCrystals

摘要

We report measurements of the thermal conductivity in a magnetic field on singlecrystals of YBa2Cu3O(7-delta). Unlike in sintered samples, the zero-field thermal conductivity of these crystals above the superconducting transition temperature shows a marked decrease with increasing temperature, demonstrating the importance of phonon-phonon processes and the high quality of the crystals. We find that the thermal conductivity K is very sensitive to the presence of fluxoids, which are strong scatters of phonons. The degradation of k is particularly large when the magnetic field H is oriented perpendicular to the Cu-O planes. The anisotropic behavior of k(H) is in qualitative agreement with a geometric argument based on the anisotropy of the superconducting coherence length. We detect hysteresis at the level of several percent in the dependence of k on the field.