THERMAL-CONDUCTIVITY OF YBA2CU3O7-DELTA IN A MAGNETIC-FIELD - CAN KAPPA(H) PROBE THE VORTEX STATE

We investigate the behavior of the thermal conductivity kappa(H) of both twinned and untwinned single crystals of YBa2Cu3O7-delta magnetic field. Remnant field data are examined in the framework of the Bean critical state model and thermally activated flux creep. In-field data are shown to depart from conventional superconductor models. The kappa(H) profile is fitted by a phenomenological form and is suggested to originate from Bloch wave travel of phonons through a vortex array which becomes more regular