Flow induced organization and memory of a vortex lattice

We report on the evolution of a vortex state in response to a driving curre nt in 2N-NbSe2 crystals. By using fast transport measurements we find that the current enables the system to reorganize and access new configurations. During this process the system exhibits a long-term memory: if the current is turned off the vortices freeze in place remembering their prior motion. When the current is restored the motion resumes where it stopped. The expe riments provide evidence for a current driven structural change of the vort ex lattice and a corresponding dynamic phase diagram that contains a previo usly unknown regime where the critical current can be either increased or d ecreased by applying current.