Separation of Quasiparticle and Phononic Heat Currents in YBCO
  Measurements of the transverse (k_{xy}) and longitudinal (k_{xx}) thermal conductivity in high magnetic fields are used to separate the quasiparticle thermal conductivity (k_{xx}^{el}) of the CuO_2-planes from the phononic thermal conductivity in YBa_2Cu_3O_{7-\delta}. k_{xx}^{el} is found to display a pronounced maximum below T_c. Our data analysis reveals distinct transport (\tau) and Hall (\tau_H) relaxation times below T_c: Whereas \tau is strongly enhanced, \tau_H follows the same temperature dependence as above T_c. 
B. Zeini (1), A. Freimuth (1), B. B\"uchner (1), R. Gross (1), A.P.   Kampf (2), M. Kl\"aser (3), and G. M\"uller-Vogt (3) (...