Vortex dynamics in regular arrays of asymmetric pinning centers

Abstract

Molecular-dynamics simulations of the current-voltage characteristics $V(I)$ have been performed for regular arrays of asymmetric pinning centers modeled by the superposition of two interpenetrating square lattices of weak and strong pinning centers with separation $\ensuremath{\Delta}p.$ In this case, an applied Lorentz force ${\mathbf{F}}_{L}$ acts as a depinning force which is directed either from weak to strong pinning site or vice versa, depending on the polarity of ${\mathbf{F}}_{L}.$ This leads to a pronounced asymmetry of the current-voltage characteristics and of the critical currents ${I}_{c}({\mathbf{F}}_{L})$ and ${I}_{c}(\ensuremath{-}{\mathbf{F}}_{L})$ (``vortex diode effect''). In addition to that, the ${F}_{L}\ensuremath{-}\ensuremath{\Delta}p$ phase diagram reveals a strong dependence of the different dynamical vortex phases on the shift between the two pinning sublattices.