Abstract
Methods are developed for modelling the effect of excitons (electron-hole bound states) on the optical properties of carbon nanotubes. The exciton effect is modelled using the methodology of the Bethe-Salpeter Equation, utilising a novel tight-binding formulation that is able to account for the effect of nanotube curvature. The exciton spectrum and fine-structure are calculated using a number of approximations to this model. The screening of excitons at high exciton density is considered by both a static and dynamic screening model; the dielectric function being modelled by the random phase approximation and the plasmon pole approximation respectively. It is shown that the static screening model significantly underestimates the stability of the exciton at high exciton densities, in comparison to experimental results, but that the results of the dynamic screening model have better agreement with experiment, and predict stability of the exciton binding energy even at high exciton densities.