Orientation-Dependent Ionic-Current Rectification in Colloidal Crystals

Nonreciprocal transport (current rectification) in bulk materials is rarer and more complex than at interfaces. We theoretically demonstrate ion current rectification in binary superlattices of oppositely charged nanoparticles and show that this effect strongly depends on the direction of the applied electric field. We derive an equation that relates the symmetry elements of the superlattice to the directions where rectification is forbidden. This equation is used to analyze the conductivity of different superlattices obtained from the numerical solution of the Poisson-Nernst-Planck equations.