Excitonic lifetimes and optical response of carbon nanotubes modulated by electrostatic gating

We investigate the excitonic optical properties of carbon nanotubes modulated by an electrostatic field applied in a direction transversal to the carbon nanotubes' axis. We find that excitation energies are redshifted while absorption peaks split due to symmetry breaking. Furthermore, from analysis of the electron-hole wave function calculated in the Wannier approximation, it is seen that the exciton wave function tends to polarize, with a separation of the electron and hole in the large-field limit. This has the effect of reducing the excitonic intrinsic radiative decay rates due to reduced electron-hole overlap. We compute thermalized effective decay rates for comparison with experiments, reflecting the interplay between exciton energy shifts and reduced intrinsic decay rates. Hence, these results suggest several possibilities for modulating the optical response of carbon nanotubes by the application of an electrostatic field in gatelike configurations.