Effects of inter-wall screening and anti-screening on excitons in double-walled carbon nanotubes

摘要

Exciton properties of double-wall carbon nanotubes are studied in the static screened Hartree-Fock approximation within an effective-mass theory. Inter-wall screening effects suppress the band gap energy and the binding energy of exciton states. As a result, the exciton energy levels are redshifted from those in the single-wall carbon nanotube with the same diameter. However, because of anti-screening effects, the behavior of excited excitons is qualitatively different from that of the ground exciton. The energy shift of the ground exciton has little dependence on the tube diameter, while that of the excited excitons decreases with the increase of the diameter, following the band gap shift.