Low-frequency electronic excitations in doped carbon nanotubes

Abstract

We study the low-frequency electronic excitations of a doped carbon nanotube. The longitudinal dielectric function, the loss function, and the plasmon frequencies are calculated within the random phase approximation. They strongly depend on the transferred momentum ( q), the transferred angular momentum ( L), the Fermi energy, and the nanotube geometry (the radius and the chiral angle). All the doped carbon nanotubes could exhibit the L=0 acoustic plasmon. There also exists the L=1 optical plasmon, when the Fermi energy is sufficiently high. There are several important differences between type-I nanotubes and type-II nanotubes. The local-field corrections on the loss spectra and the plasmon frequencies are discussed.