Surface Instabilities and Plastic Deformation of Vortex Lattices

We investigate the stability of the vortex configuration in thin superconducting strips under an applied current analytically and by numerical simulations of the time-dependent Ginzburg-Landau equation. We show that the stationary vortex lattice becomes unstable with respect to long-wavelength perturbations above some critical current I_c. We find that at currents slightly exceeding I_c the vortex phase develops plastic flow, where large coherent pieces of the lattice are separated by lines of defects and slide with respect to each other (ice-floe-like motion). At elevated current a transition to elastic flow is observed.