A magnetic field is found to have strong effects on the electronic structure and bulk properties of carbon nanotubes. A field-induced metal-insulator transition is predicted for all pure nanotubes. In a weak field, nanotubes exhibit both large diamagnetic and paramagnetic responses depending on the field direction, the Fermi energy, the helicity, and the nanotube radius. Universal scalings are found in the susceptibility as functions of the Fermi energy, the temperature, and the size of nanotubes. Comparison with recent experiments are discussed.

• Received 18 July 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.1123