Diameter-dependent conductance oscillations in carbon nanotubes upon torsion.

Torsion-induced conductance oscillations have been recently observed in multi-wall carbon nanotubes$^{1,2}$. These oscillations have been interpreted as metal-semiconductor periodic transitions, while an alternative interpretation attributed the phenomenon to changes in registry between the walls. Here we show$^{3}$ that the period of the oscillations is inversely proportional to the squared diameter of the nanotube (\textit{$\delta \phi \sim $1/d}$^{2})$. This dependence is theoretically predicted from the shifting of the corners of the first Brillouin zone of graphene across different subbands allowed in the nanotube, whereas a change in registry should give rise to a simple inverse dependence (\textit{$\delta \phi \sim $1/d}). Hence, the experimental results validate the interpretation of Fermi level shift across subbands \textit{vs}. that of registry change, as a source of torsion-induced conductance oscillations in carbon nanotubes. \newline \newline [1] T. Cohen-Karni \textit{et al}, Nature Nanotech. \textbf{1}, 36 (2006). \newline [2] E. Joselevich, ChemPhysChem \textbf{7}, 1405 (2006). \newline [3] K. S. Nagapriya \textit{et al}, \textit{in preparation}.