Depinning and dynamics of ac driven vortex lattices in random media

Abstract

We study the different dynamical regimes of a vortex lattice driven by ac forces in the presence of random pinning via numerical simulations. The behavior of the different observables is characterized as a function of the applied force amplitude for different frequencies. We discuss the inconveniences of using the mean velocity to identify the depinning transition and we show that instead, the mean quadratic displacement of the lattice is the relevant magnitude to characterize different ac regimes. We discuss how the results depend on the initial configuration and we identify hysteretic effects which are absent in the dc driven systems.