Metallic single-walled carbon nanotubes (SWNTs) do not behave like normal metallic wires. In normal metallic wires the number of open conduction channels (states at the Fermi level) will increase as the cross-section of the wire increases. In contrast, the number of channels available for conduction in metallic SWNTs is independent of the tube's diameter . We will discuss how this key property of metallic SWNTs allows them to avoid the spontaneous symmetry breaking that converts other potentially excellent metallic nanowires into semiconductors . We will also discuss how this property is central to the ability of metallic and semimetallic SWNTs to sustain ballistic transport over unprecedented distances for such laterally confined systems in the presence of residual chemical and structural disorder . Thus, it is the fixed number of states at the Fermi level, which when combined with their mechanical and chemical stability and the strong C-C interactions along the tube, that makes metallic and semimetallic SWNTs strong candidates for the ultimate one-dimensional conductors for use in nanoscale devices. Finally, we touch upon recent results that indicate that semimetallic nanotubes will find use as electromechanical gauges.
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