Signature of chirality in scanning-probe imaging of charge flow in graphene

We theoretically propose to directly observe the chiral nature of charge carriers in graphene mono- and bilayers within a controlled scattering experiment. The charge located on a capacitively coupled scanning-probe microscope (SPM) tip acts as a scattering center with controllable position on the graphene sheet. Unambiguous features from the chirality of the particles in single and bilayer graphene arise in the ballistic transport in the presence of such a scattering center. To model the scattering from the smooth potential created by the SPM tip, we derive the space-dependent electron Green function in graphene and solve the scattering problem within the first-order Born approximation. We calculate the current through a device with a SPM tip between two constrictions (quantum point contacts) as a function of the tip position.