Equilibration and dynamic phase transitions of a driven vortex lattice

We report on the observation of two types of current driven transitions in metastable vortex lattices. The metastable states, which are missed in usua l slow transport measurements, are detected with a fast transport technique in the vortex lattice of undoped 2H-NbSe2. The transitions are seen by fol lowing the evolution of these states when driven by a current. At low curre nts we observe an equilibration transition from a metastable to a stable st ate, followed by a dynamic crystallization transition at high currents.