Competition between intertube interactions and external electric fields on a pair of narrow-gap carbon nanotubes

A uniform transverse electric field is applied to a pair of narrow-gap carbon nanotubes with intertube interactions, and the electronic structures at low energy are studied within the tight-binding model. Unlike a single nanotube, the band structures of an aligned pair vary with not only the strength of the electric field but its direction. When the transverse field is applied along the plane containing both tube axes of the pair, the low energy bands are found to have significant changes with the field strength higher than View the MathML source, only a tenth of the order for a single tube. A small energy gap could be opened by the intertube interactions, nevertheless, the hybridization of atomic wave functions between tubes is suppressed by increasing the electric field. By contrast, a field perpendicular to the plane of tube axes alters the band structures at the same level as for a single tube, and the electronic states between tubes are still strongly coupled.