INDIVIDUAL SINGLE-WALL CARBON NANOTUBES AS QUANTUM WIRES

Carbon nanotubes have been regarded since their discovery(1) as potent ial molecular quantum wires. In the case of multi-wall nanotubes, wher e many tubes are arranged in a coaxial fashion, the electrical propert ies of individual tubes have been shown to vary strongly from tube to tube(2,3), and to be characterized by disorder and localization(4). Si ngle-wall nanotubes(5,6) (SWNTs) have recently been obtained with high yields and structural uniformity(7). Particular varieties of these hi ghly symmetric structures have been predicted to be metallic, with ele ctrical conduction occurring through only two electronic modes(8-10). Because of the structural symmetry and stiffness of SWNTs, their molec ular wavefunctions may extend over the entire tube. Here we report ele ctrical transport measurements on individual single-wall nanotubes tha t confirm these theoretical predictions. We find that SWNTs indeed act as genuine quantum wires, Electrical conduction seems to occur throug h well separated, discrete electron states that are quantum-mechanical ly coherent over long distance, that is at least from contact to conta ct (140 nm), Data in a magnetic field indicate shifting of these,state s due to the Zeeman effect.