Thermal transport in high-T-c crystals: Some aspects on its temperature and magnetic field dependence

We have measured the temperature (10 K less than or equal to T less than or equal to 150 K) and magnetic field (B less than or equal to 9T) dependence of the in-plane thermal conductivity kappa(T,B) of YBa2Cu3O7-x (Y123), YBa 2Cu4O8 (Y124), and Bi2Sr2CaCu2O8 (Bi2212) high-temperature superconducting crystals, at different orientations of the magnetic field (B parallel to c and perpendicular to c). Our results show that hr depends on field below an d above the critical temperature due to the contribution of superconducting fluctuations and of vortices and orbital effects to the scattering of quas iparticles or electrons. Within experimental resolution no dimensional cros sover of the superconducting fluctuations can be clearly recognized Qualita tive and quantitative differences in the field dependence between the cryst als are observed and discussed We argue that the anisotropy plays a mayor r ole in the relative weight between the different scattering processes and t he field effect on the occupation number of quasiparticles, determining the field dependence of the thermal conductivity in these cuprates. In particu lar we found that kappa increases with field in a Bi2212 crystal for B perp endicular to c and at T < 20 K.