Probing optical spectra of carbon nanotubes with external fields

Here we present a theoretical study of the interplay between electronic and optical properties of carbon nanotubes. External perturbations such as electric and magnetic fields are applied on the systems which are probed by parallel and perpendicularly polarized light sources. We demonstrate that the optical transitions can be fully controlled by the fields. Likewise, extra optical excitations can be induced in different energy ranges of the absorption spectra due to degeneracy splitting of the states. In most of the theoretical works developed in this realm, a remarkable discrepancy between the results obtained via the tight binding approximation and first principle calculations is found. The disagreement can be enhanced when external perturbation fields act on the tubes forcing the realization of demanding charge self-consistent calculations. In this sense, we profit from novel parametrization schemes for the tight binding approach to describe the optical response of nanotubes of any diameter size and with similar accuracy to density functional theory.