Effects of magnetic field and disorder on the electronic properties of carbon nanotubes

The electronic properties of carbon nanotubes are investigated in the presence of a magnetic field perpendicular to the nanotube axis and disorder introduced through site-energy randomness. The magnetic field is shown to induce a metal-insulator transition for the metallic $\mathrm{}(9,0),(12,0)\mathrm{}\dots$ nanotubes in the absence of disorder. It is also shown that semiconducting nanotubes can become metallic with increasing magnetic strength. The low disorder limit preserved the electronic structure whereas the metal-insulator transition remains even in the strong disorder limit. These results may find experimental confirmation with tunneling spectroscopy measurements.