Righi-Leduc effect in Y- and Bi-based high-T-c superconductors

Measurements of the transverse (k(xy)) and longitudinal (k(xx)) thermal con ductivity in the superconducting state of single crystals of YBa2Cu3O7-delt a (YBCO) and Bi2Sr2CaCu2O8-delta (BSCCO) are presented in applied magnetic fields up to 14 T. We separate the electronic thermal conductivity (k(xx)(e l)) of the CuO2-planes from the phononic thermal conductivity (k(xx)(ph)) u sing k(xy) and the magnetic field dependence of k(xx). Our main results are : (1) Tn YBCO k(xx)(el)(T) shows a pronounced maximum. We attribute this to a rapid increase of the quasiparticle scattering time tau below T-c. The m aximum of k(xx)(el)(T) in BSCCO is much smaller due to stronger impurity sc attering. The maximum of k(xx) is strongly suppressed by a magnetic field, presumably because of scattering of QPs on vortices. (2) Our data analysis reveals that below T-c a transport (tau) and Hall (tau(H)) relaxation time must be distinguished as in the normal state. Whereas tau is strongly enhan ced below T-c, tau(H) displays the same temperature dependence as above T-c . (C) 1999 Elsevier Science B.V. All rights reserved.