Hidden one-electron interactions in carbon nanotubes revealed in graphene nanostrips

Many single-wall carbon nanotube (SWNT) properties near the Fermi level were successfully predicted using a nearest-neighbor tight-binding model characterized by a single parameter, V-1. We show however that this model fails for armchair-edge graphene nanostrips due to interactions directly across hexagons. These same interactions are found largely hidden in the description of SWNTs, where they renormalize V-1 leaving previous nearest-neighbor model SWNT results largely intact while resolving a long-standing puzzle regarding the magnitude of V-1.