Ultraviolet π -plasmon contribution to the transverse optical response of doped single-walled carbon nanotubes

A model for the effective permittivity of a doped single-walled carbon nanotube (CNT) thin film in the optical range is proposed. The permittivity of CNT walls is calculated from the quantum theory of π-electron transitions. The contributions from σ electrons and ultraviolet π plasmon are taken into account phenomenologically using experimental data obtained for graphene and CNT film. These contributions lead to an enhancement of the depolarization effect thereby strongly suppressing the transverse response of the CNTs. They also cause a decrease in both the frequency and height of the absorption peak associated with the azimuthal intersubband plasmon in doped CNTs. This eliminates the existing discrepancy between experimental and previous theoretical data. The azimuthal plasmon response is studied in a bundle of doped CNTs.