Self-energy corrections to DFT-LDA gaps of realistic carbon nanotubes

Since their discovery carbon nanotubes have attracted much interest for their peculiar electronic properties which go from metallic to semiconducting behaviour, depending both on diameter and chirality. The exact value of their band gap is obviously a crucial point to be addressed because it enters in the nanotube application as microelectronic devices. By making use of an efficient GW scheme, previously tested on bulk systems, as well as of a model screening function, we obtained for the first time excitation energies and band-gap values for carbon nanotubes. Results for (6, 0) and (7, 0) will be presented and discussed.