QUANTUM TRANSPORT IN A MULTIWALLED CARBON NANOTUBE

We report on electrical resistance measurements of an individual carbo n nanotube down to a temperature T = 20 mK. The conductance exhibits a lnT dependence and saturates at low temperature. A magnetic field app lied perpendicular to the tube axis increases the conductance and prod uces aperiodic fluctuations. The data find a global and coherent inter pretation in terms of two-dimensional weak localization and universal conductance fluctuations in mesoscopic conductors. The dimensionality of the electronic system is discussed in terms of the peculiar structu re of carbon nanotubes.