Spatially resolved edge currents and guided-wave electronic states in graphene

Exploiting the light-like properties of carriers in graphene could allow extreme non-classical forms of electronic transport to be realized(1-8). In this vein, finding ways to confine and direct electronic waves through nanoscale streams and streamlets, unimpeded by the presence of other carriers, has remained a grand challenge(9-12). Inspired by guiding of light in fibre optics, here we demonstrate a route to engineer such a flow of electrons using a technique for mapping currents at submicron scales. We employ real-space imaging of current flow in graphene to provide direct evidence of the confinement of electron waves at the edges of a graphene crystal near charge neutrality. This is achieved by using superconducting interferometry in a graphene Josephson junction and reconstructing the spatial structure of conducting pathways using Fourier methods(13). The observed edge currents arise from coherent guided-wave states, confined to the edge by band bending and transmitted as plane waves. As an electronic analogue of photon guiding in optical fibres, the observed states afford non-classical means for information transduction and processing at the nanoscale.