Loss of translational symmetry in carbon nanotubes

The loss of translational symmetry at the ends of a carbon nanotube has a non-trivial effect on its ballistic conductance. Capping an armchair nanotube at one end leads to the loss of one ballistic conductance channel. This explains recent experimental findings of S. Frank, P. Poncharal, Z.L. Wang, W.A. de Heer [Science 280 (1998) 1744]. The loss of translational symmetry is not accompanied by the localization of states at the open ends of an armchair nanotube. This contrasts with the zigzag case where localized end-states do occur. This behavior derives from the properties of the corresponding infinite nanotubes.