ELECTRON-THERMAL AND PHOTON-THERMAL CONDUCTIVITY OF HIGH-T-C SYSTEMS FROM THE UNDERDOPED INSULATING TO THE NONSUPERCONDUCTING METALLIC PHASE

Thermal conductivity kappa of La2-ySryCu1-xZnxO4 and Bi1.6Pb0.5Sr1.9-y LayCuO6, in which the electron-number density can he controlled from t he underdoped insulating to the nonsuperconducting metallic phase thro ugh the superconducting one, has been measured. By considering the sys tematic difference of the T-dependences of kappa among above three pha ses, the observed kappa has been consistently divided into the electro n-and phonon-components. In the superconducting phase, the T-dependenc e of the electron component is found to support the d-symmetry of the order parameter.