Contact resistance of quantum tubes

We consider the conductance of a quantum tube connected to a metallic conta ct. The number of angular momentum states that the tube can support depends on the strength of the radial confinement. We calculate the transmission c oefficients which yield the conductance via the Landauer formula, and discu ss the relation of our results to armchair carbon nanotubes embedded in a m etal. For Al and Au contacts and tubes with a realistic radial confinement we find that the transmission can be close to unity corresponding to a cont act resistance close to h/2e(2) per band at the Fermi level in the carbon n anotube. (C) 1999 Academic Press.