Peak effect and the transition from elastic to plastic depinning

We demonstrate for the first time an observation of the peak effect in simulations of magnetic vortices in a superconductor. The shear modulus c(66) of the vortex lattice is tuned by adding a fictitious attractive short-range potential to the usual long-range repulsion between vortices. The peak effect is found to be most pronounced in low densities of pinning centers, and is always associated with a transition from elastic to plastic depinning. The simulations suggest in some situations that over a range of values of c(66) the production of lattice defects by a driving force enhances the pinning of the lattice.