Rocking ratchets in 2D Josephson networks: collective effects and current reversal

TL;DR

This paper investigates how ac-driven vortices in 2D Josephson junction arrays with asymmetric pinning potentials exhibit directed motion and current reversal, revealing collective effects and vortex density dependence through detailed numerical simulations.

Contribution

It provides a comprehensive numerical analysis of vortex dynamics in 2D Josephson arrays, highlighting the collective mechanisms behind current reversal and the influence of vortex density.

Findings

Current reversal depends on vortex density and ac amplitude.

Vortex flow direction can invert, matching experimental observations.

Collective vortex interactions are key to understanding the effect.

Abstract

A detailed numerical study on the directed motion of ac-driven vortices and antivortices in 2D Josephson junction arrays (JJA) 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 Shal\'om and Pastoriza [Phys. Rev. Lett. {\bf 94}, 177001 (2005)]. 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.