Resonant transmission through finite-sized carbon nanotubes - art. no. 155412

We have investigated theoretically the conductance through finite-sized car bon nanotubes coupled to featureless leads in the context of standard tight -binding models. Conduction takes place via resonant tunneling, and the res ultant spectrum of peaks may be understood in terms of the band structure o f the nanotubes. Specific nanotubes display both on- and off-resonance beha vior as a function of nanotube length depending upon whether or not the ban ds cross at a nonzero I;value. We have also investigated the approach to th e infinite limit in detail, and, in general, And that the finite-size effec ts can persist out to hundreds of nanometers. Since the manipulation of nan otubes into devices is likely to induce defects, we have investigated their effects on the conduction. The effects of bending and two broad classes of defects, i.e., defect in the absence and/or presence of addimers, were con sidered. In general, the presence of defects leads both to a reduction and shifting of the resonant peaks at the Fermi level. However, in the infinite limit, low concentrations of defects have only a relatively modest effect on the transport properties. Finally, we have investigated the effects of a n externally imposed magnetic field oriented perpendicular to the nanotube axis. The magnetic field shifts the levels, thereby turning on- and off-res onant devices into each other. All of the effects discussed here are testab le experimentally.