Energy spectrum and optical properties of infinite carbon nanotubes in the Hubbard model

Abstract

The energy spectra of carbon nanotubes with chiralities (5, 5) and (10, 0) have been calculated in terms of the Schubin-Wonsowskii-Hubbard model. It has been shown that, in contrast to the generally accepted concept, all the carbon nanotubes, regardless of their chirality, are semiconductors with an energy gap of the order of 1 eV. The optical absorption spectra of the systems under investigation have been calculated using the obtained energy spectra. It has been found that, in the optical absorption spectra, there are peaks at energies of 1.04, 1.28, 2.05, 3.16, 4.38, 5.05, and 5.78 eV for carbon nanotubes with the (5, 5) chirality and peaks at energies of 1.03, 1.30, 1.85, 2.77, 3.87, 5.00, 5.72, 6.20, and 6.60 eV for carbon nanotubes with the (10, 0) chirality. The obtained results have been compared with the experimental data. The conclusion has been drawn that no significant (critical) differences in the optical absorption spectra of the carbon nanotubes with chiralities (5, 5) and (10, 0) are observed.