Localization of electronic states by fullerene charges in carbon   nanotubes
  We study the effects of the electrostatic interaction produced by charged fullerenes encapsulated in carbon nanotubes, showing that they are able to modify locally the electronic density of states in the hybrid system. In the cases where the interaction is felt as an attractive potential by the electrons in the nanotube, localized electronic states are formed in the nanotubes around the position of the fullerenes. This produces an effective narrowing of the gap in semiconducting nanotubes over a distance of a few nanometers, in agreement with the spatial modulation of the gap observed in the experiments. 
J. Gonzalez and F. Guinea