High-frequency vortex dynamics in YBa2Cu3O7

We present a phenomenological description of the high-frequency vortex dynamics in YBa2Cu3O7 and discuss the main parameters related to vortex motion, namely the viscous drag coefficient eta, the pinning constant K-p (Labusch parameter) and the depinning frequency omega(0). We demonstrate experimental results on the angular and temperature dependence of eta, K-p and omega(0) in YBa2Cu3O7 and compare these results with existing models. We show how studies of the vortex viscosity may yield information on the superclean limit. This limit corresponds to the formation of the discrete excitation spectrum in the vortex core due to quantum confinement and small coherence length. From the low-temperature viscosity data we conclude that the superclean limit in YBa2Cu307 is reached for magnetic field perpendicular to the c-axis.