Two-dimensional vortex dynamics in YBa2Cu3O7/PrBa2Cu3O7 multilayers.

We have measured the current-voltage characteristics of an YBa 2 Cu 3 O 7 /PrBa 2 Cu 3 O 7 multilayer in perpendicular magnetic fields. A dislocation-mediated melting behavior of the two-dimensional vortex lattice (VL) is identified. Below the melting field, the vortex motion is found to undergo a crossover from elastic motion to plastic motion when the activation energy for the collective creep exceeds the formation energy of dislocation pairs in the VL at low currents. Above the melting field, the vortices are in a pinned liquid state with the I-V curves characterized by a linear behavior at small currents, changing to a nonlinear behavior at large currents