Our early theoretical work predicted that carbon nanotubes should be metallic. Tans et al. have confirmed these predictions and showed that coherent transport can be maintained through these nanowires up to distances of at least 140 nm. But single-walled armchair nanotubes are one-dimensional with only two open conduction channels at the Fermi level. Hence, with increasing length their conduction electrons will ultimately become localized due to any residual disorder present in the tube. We show however that unlike normal metallic wires, electrons in armchair nanotubes experience an effective disorder averaged over the tube diameter leading to electron mean free paths that increase with the nanotube diameter. This scaling rule - supported by numerical calculations - together with the mechanical stability of the tube and the strong C-C interactions along the tube results in exceptional ballistic transport properties and long localization lengths along the tube for armchair tubes with diameters that are typically produced experimentally. The rapidly developing area of carbon nanotubes implies a major role for these nanowires as components in 21st century electronic devices.
Code 6189, Naval Research Laboratory
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