Effects of trigonal warping on perfect channel in metallic carbon nanotubes

Numerical calculations of the conductance are performed to study effects of trigonal warping of bands on a perfectly conducting channel in metallic carbon nanotubes existing unless the potential range of scatterers is smaller than the lattice constant. The perfect channel can easily be destroyed in the presence of small amount of trigonal warping when there are several bands at the energy, while it is much more robust in the energy range of metallic linear bands.