Thickness dependence of vortex critical velocity in wide Nb films

Pulsed I–V measurements performed on wide Nb films of different thickness show the electronic instability, at high driving currents, predicted by Larkin and Ovchinnikov (LO). We find that the associated vortex critical velocity v∗ decreases with the film thickness, and its temperature and magnetic field dependences exhibit some discrepancies with respect to the LO theoretical results.