Electronic properties of single-walled carbon nanotubes under electric and magnetic fields

The sp3 tight-binding model, with the nearest-neighbor interactions, is used to calculate electronic structures of single-walled carbon nanotubes under uniform transverse electric fields and magnetic fields with gazing angles. The external fields strongly affect energy dispersions, energy gap, band-edge states, state degeneracy, and subband spacings. They make semiconducting carbon nanotubes exhibit the semiconductor-metal transitions. The changes of band structures are directly reflected on the features of density of states (DOS). The electric and magnetic fields alter the heights, positions and number of the prominent peaks in DOS.