EFFECT OF THE PHONON-ELECTRON INTERACTION ON ANISOTROPY IN THE THERMAL-CONDUCTIVITY OF YBCO CRYSTALS

Experimental results on the anisotropic thermal conductivity kappa for the directions of the a-, b- and c-axis in YBCO crystals, have been a nalyzed comprehensively to make clear the mechanism of the high T-c su perconductivity. By comparing these results to the Tewordt and Wolkhau sen (T-W) theory, the anisotropic phonon-carrier interaction coefficie nts gamma(a), gamma(b), and gamma(c) are evaluated. It is concluded th at gamma a greater than or equal to gamma(b) > gamma(c), and the large r the value of gamma in a direction, the higher the density of the Coo per pairs in that direction. From the maximum increment of kappa below T-c, Delta kappa, at each direction, phonons are concluded to be much more mobile along the ab-plane than along the c-axis.