EXPERIMENTS ON THE JOSEPHSON PLASMA MODE IN BI2SR2CACU2O8 AND THE THERMAL HALL CONDUCTIVITY IN YBA2CU3O7

The Josephson plasma mode has been observed directly in Bi2Sr2CaCu2O8 using microwave radiation in the 30 to 90 GHz range. Measurements in a n oblique field provide rather conclusive evidence for the plasma osci llations, as well as a determination of the anisotropy parameter gamma . In a second experiment, we discuss how the mean free path l(0) of qu asi-particles may be measured using asymmetric scattering off pinned v ortices. In 90-K YBa2Cu3O7, we find that l(0) increases rapidly from 9 0 Angstrom at 100 K to 2500 Angstrom at 15 K.