Conductance through graphene bends and polygons

We investigate the transmission of electrons between conducting nanoribbon leads oriented at multiples of 60 degrees with respect to one another, connected either directly or through graphene polygons. A mode-matching analysis suggests that the transmission at low energies is sensitive to the precise way in which the ribbons are joined. Most strikingly, we find that armchair leads forming 120 degrees angles can support either a large transmission or a highly suppressed transmission, depending on the specific geometry. Tight-binding calculations demonstrate the effects in detail and are also used to study transmission at higher energies as well as for zigzag ribbon leads.