Effects of environmental dielectric screening on optical absorption in carbon nanotubes

Effects of environmental dielectric screening on optical absorption spectrum are studied in carbon nanotubes within a k·pk·p scheme. The screening is sensitive to the effective distance between the nanotube and the dielectric medium. For material surrounding the nanotube, the band gap decreases with the increase of the dielectric constant, but the energy of the ground exciton exhibits only a slight decrease for effective distance comparable to interlayer spacing of bulk graphite. For dielectric material inside the nanotube, effects are much weaker because of anti-screening.