LOW-TEMPERATURE BEHAVIOR OF THE THERMAL-CONDUCTIVITY OF HIGH-T-C SUPERCONDUCTORS - LIKELINESS OF D(X(2)-Y(2)) WAVE PAIRING

We consider the temperature dependence of the thermal conductivity of high-T-c superconductors with a superconducting gap parameter of eithe r s-wave or d(x2-y2)-wave type, respectively. We compare the theoretic al results at low temperatures within a Lawrence-Doniach model for the energy spectrum. The previously reported low-temperature behaviour of the thermal conductivity of La2-xSrxCuO4, YBa2Cu3O7-delta, Bi2Sr2CaCu 2O8 and Tl2Ba2Ca2Cu3O10 compounds is analysed. We show that this behav iour is inconsistent with an isotropic s-wave gap parameter but can be explained by assuming that the symmetry of the gap parameter is of d( x2-y2) type.