Controlling directed transport in two-dimensional periodic structures under crossed electric fields

We investigate different mechanisms for the control of directed transport of particles on two-dimensional periodic and symmetric substrates, based on the application of a crossed static and a bi-harmonic (harmonic mixing) field. We focus on inertial systems in the low friction regime, using a prototypical model for atom-surface diffusion, and demonstrate that a proper control of current reversals can be achieved at moderate field strengths by tuning either the static field or changing the relative phase of the harmonic mixing signal, respectively. (C) 2004 Elsevier B.V. All rights reserved.