2-DIMENSIONAL VORTEX DYNAMICS IN YBA2CU3O7 PRBA2CU3O7 MULTILAYERS/

We have measured the current-voltage characteristics of an YBa2Cu3O7/P rBa2Cu3O7 multilayer in perpendicular magnetic flelds. A dislocation-m ediated melting behavior of the two-dimensional vortex lattice (VL) is identified. Below the melting field, the vortex motion is found to un dergo a crossover from elastic motion to plastic motion when the activ ation 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 charact erized by a linear behavior at small currents, changing to a nonlinear behavior at large currents.