Absorption-spectral features of single-walled carbon nanotubes

We present a visual, intuitive connection between optical absorption line shapes and the underlying carbon nanotube structures. Within the tight-binding model, the absorption spectra can be linked directly to plots of energy contours and transition dipoles of a graphene sheet. Via two additional approaches, spectral features are shown only slightly altered by electronic correlations and sigma-pi orbital rehybridization. Despite dependence of electronic structures on chiral angles, it is proved that, if the tube diameter D is greater than the C-C bond length a, the absorption spectra are determined by D to the lowest order in a/D. (C) 2004 Elsevier B.V. All rights reserved.