Interwall screening and excitons in double-wall carbon nanotubes

Abstract

Exciton properties of double-wall carbon nanotubes are studied in the static screened Hartree-Fock approximation within a k•p scheme. The intrawall electron-hole interaction is largely suppressed by interwall screening effects. The suppression is sensitive to the effective interwall distance between the inner and outer tubes and reduces the exciton binding energy as well as the band gap. As a result, the exciton energy levels are redshifted from those in the single-wall tube with the same diameter. The energy shift of the ground exciton has little dependence on the tube diameter, in contrast to that of the excited excitons. In the case of a metallic outer and inner tube, excited exciton states in the semiconducting tube disappear due to strong screening. © 2012 American Physical Society.