Optical excitations of finite double-walled carbon nanotubes under electric field

The optical spectra of finite double-walled carbon nanotubes under electric field are investigated by the tight-binding model. Both intertube interactions and electric fields can cause drastic changes in the symmetry of the states, the Fermi level, energy spacing, and state degeneracy. However, while an electric field leads to state crossing and more low-energy states, intertube interactions can make absorption peaks of single-walled carbon nanotubes separate into either two or more peaks. The number, the intensity, and the frequency of absorption peaks would be modulated by the electric field. There exists a competition between the electric field and the intertube interactions. Moreover, there are less absorption peaks when the electric field is parallel to the nanotube axis. (C) 2009 Elsevier B.V. All rights reserved.