Anderson localization in semiconducting carbon nanotubes

We have calculated the conductance in semiconducting carbon nanotubes containing randomly distributed impurity potentials under magnetic fields, where Anderson localization takes place in contrast to the ballistic transport in metallic nanotubes. We have found that the magnetic flux enhances the conductance showing large negative magnetoresistance, while the magnetic field perpendicular to the tube axis gives slight reduction of the conductance giving much smaller positive magnetoresistance.