Vortex density waves and negative absolute resistance in patterned superconductors

We study theoretically dynamical phases of vortices in superconducting films with arrays of obstacles. By performing a series of molecular dynamics simulations and analytical calculations, we demonstrate the existence of a phase of soliton-like vortex-density waves appearing in a wide range of parameters. These waves are formed by a self-assembled phase separation process induced by strongly nonlinear density fluctuations of the moving vortex matter above a certain critical driving current. At high vortex concentrations, the waves move at an approximately current-independent speed resulting in a wide plateau in the voltage-current characteristics. At stronger drives, the vortex system enters into a fully jammed (zero-voltage) phase. By combining ac and dc drives, the interplay between the vortex-density-wave and jammed phases leads to the observation of negative absolute mobility of vortices, which induces the superconducting film into a negative resistance state.