title: Rocking ratchets in two-dimensional Josephson networks: collective effects and current reversal.
abstract: A detailed numerical study on the directed motion of ac-driven vortices and antivortices in 2D Josephson junction arrays with an asymmetric periodic pinning potential is reported. dc-voltage rectification shows a strong dependence on vortex density as well as an inversion of the vortex flow direction with ac amplitude for a wide range of vortex density around f = 1/2 (f = Ha(2)/Phi(0)), in good agreement with recent experiments by Shalóm and Pastoriza [Phys. Rev. Lett. 94, 177001 (2005)10.1103/PhysRevLett.94.177001]. The study of vortex structures, spatial and temporal correlations, and vortex-antivortex pairs formation gives insight into a purely collective mechanism behind the current reversal effect.
authors.affiliation: Institut de Physique, Université de Neuchâtel, CH-2000 Neuchâtel, Switzerland.
authors.forename: Verónica I
authors.initials: VI
authors.lastname: Marconi