Homogeneous nanocables from double-walled boron-nitride nanotubes using first-principles calculations

Since electrons injected to a homogenous wire always tend to concentrate on its surface, heterogeneous coaxial structures are generally necessary to make nanocables with an insulating sheath. Here we reveal from first-principles calculations that double-walled boron-nitride nanotubes could be natural homogeneous nanocables as injected electrons prefer abnormally to concentrate on the inner semiconducting tube while the outer tube remains insulating. The ratio of extra electrons on the inner tube to total carriers in the double-walled nanotubes can be tuned widely by changing either the tube diameter or the local tube curvature through radial deformation, both attributed to the predominant band filling and weak enhancement in Coulomb interaction within the inner wall where the sublattice asymmetry is strongly attenuated by curvature effect. This exotic charge screening is universal for any form of electron-doping sources.