THE EUROPEAN PHYSICAL JOURNAL B – CONDENSED MATTER AND COMPLEX SYSTEMS 34, 135 (2003)

R. Ocaña and P. Esquinazi

Abstract

The angle dependence at different temperatures of the longitudinal thermal conductivity xx() in the presence of a planar magnetic field is presented. In order to study the influence of the gap symmetry on the thermal transport, angular scans were measured up to a few Kelvin below the critical temperature T_c. We found that the four-fold oscillation of xx() vanishes at T > 20K and transforms into a one-fold oscillation with maximum conductivity for a field of 8 T applied parallel to the heat current. Nevertheless, the results indicate that the d-wave pairing symmetry remains the main pairing symmetry of the order parameter up to T_c. Numerical results of the thermal conductivity using an Andreev reflection model for the scattering of quasiparticles by supercurrents under the assumption of d-wave symmetry provide a semiquantitative description of the overall results.