Vortex dynamics and symmetry locking on quasiperiodic and periodic substrates

Abstract

We examine the dynamics of vortices driven over quasicrystalline and periodic pinning arrays where the direction of the external drive is varied with respect to the substrate orientation. For periodic arrays there is a strong directional locking and the vortex motion can lock to symmetry directions of the pinning lattice even when the drive is not applied along the same symmetry direction. This locking can be detected as a series of steps in the velocity vs driving angle curves and is also associated with dynamical ordering of the vortices along these steps into anisotropic square and triangular lattices. Even though quasicrystalline arrays lack translational order, we show that quasicrystalline substrates also exhibit symmetry locking due to their orientational ordering. The vortex configurations in the nonlocking regimes are much more disordered for the quasiperiodic substrates than for the periodic substrates.