Imaging Dirac fermions flow through a circular Veselago lens

Abstract

Simulations and experiments are combined to visualize current density through a circular graphene $p\phantom{\rule{0}{0ex}}n$ junction, formed by biasing the metallic tip of an atomic force microscope. To image current density, the tip is moved around a graphene constriction, acting as a detector probing a subset of trajectories depending on the tip position with respect to the constriction. The results reveal the crucial role of junction smoothness on current focusing and anti-focusing, thereby establishing the technique as a new tool for electron optics in graphene.