Ab initio calculations show that the band gap of boron nitride (BN) nanotubes can be greatly reduced by a transverse electric field. This gap reduction arises from a mixing of states within the highest occupied molecular orbital and lowest unoccupied molecular orbital complexes and leads to a spatial separation of electrons and holes across the tube diameter. The gap modulation increases with tube diameter and is nearly independent of chirality. For BN nanotubes of diameters of 5 nm or more, a sizable gap reduction should be achievable with laboratory fields. This effect provides a possible way to tune the band gap of BN tubes for various applications.

• Received 24 October 2003

DOI:https://doi.org/10.1103/PhysRevB.69.201401