Electronic transport in intermediate sized carbon nanotubes

We have measured low temperature transport properties of multiwalled carbon nanotubes (MWNT) of different diameters in the range 2-10 nm [1]. In nearly all samples the gate dependent conductance exhibits a gap whose size increases with decreasing tube diameter and increasing electrode separation. This so called transport gap is attributed, based on the experimental findings, on a combination of localization effects and narrow diameter induced gaps in the electronic band structure. \\[4pt] [1] M. Ahlskog, O. Herranen, A. Johansson, J. Lepp\"{a}niemi, and D. Mtsuko, Phys. Rev. B \textbf{79}, 155408 (2009).