Controlled vortex motion in multiple interpenetrating pinning arrays

Abstract

We study the effect of multiple interpenetrating pinning arrays on the vortex motion in the presence of an ac driving force, f d (t), by using extensive molecular dynamics (MD) simulations. Firstly, the response to a square ac wave f d (t) has been explored for the vortices interacting with a periodic square pinning array which has different pinning strengths and sizes. The effect of the type of an ac drive and its amplitude on the oscillatory dynamics of vortices have been investigated in detail. For very low displacements of the vortices, we have found that the single-particle model can produce results analytically similar to the ones obtained by the MD simulations. It is shown that the collective motion of vortices can be controlled easily by varying the number of multiple interpenetrating square pinning lattices (N SPSL). A regular sequence of peaks has been observed for N SPSL = 3 in the time evolution of the average velocity of the vortices (i.e., V x - t curves). The number of peaks (N peak) strongly depends on the magnitude of f d (t), and increases with increasing the magnitude of f d . The close relation between N peak and f d is considered as an indication of controlling vortex motion in a multiple periodic pinning structure. Finally, the variation of the power spectrum of noise S(ν) with N SPSL has been investigated. For N SPSL = 3, it has been found that the plastic motion of the row of vortices evolves at low frequencies, i.e., 1/ν behavior, whereas, at high frequencies, S(ν) shows a typical behavior of Gaussian white noise.