Anisotropic dynamics of charge carriers in graphene

Computer simulation by numerically solving thetime-dependent Schrodinger equation was used to investigate the spreading of electronic wave packets on the graphene surface injected from a local probe. The simulations show a highly anisotropic in-plane dynamics following a 60 degrees angular periodicity even near the Fermi energy. The wave packet first tunnels onto the small graphene clusters below the tip and the electronic states of these clusters govern the further spreading of the electron on the graphene surface. It was found that in the vicinity of the injection point the molecular physical behavior dominates, but at larger distances the wave propagation is governed by solid-state physical rules. The calculations show complex charge-spreading phenomena at graphene grain boundaries. Our results reveal a new picture of charge propagation in graphene, which has important consequences for nanoelectronic applications.