Plasmon excitations of single-wall carbon nanotubes

Abstract

Plasmon excitations in isolated single-wall carbon nanotubes are singled out in the optical spectra, and analyzed within density-functional tight-binding method and random-phase approximation. Full symmetry considerations, implemented in both approaches, stressed out that only helical quantum numbers are conserved in processes involving momentum transfer, i.e., only these quantum numbers can be unambiguously attributed to the plasmons. Energy of π plasmon is about 5 eV and slightly decreases with diameter with no observable influence of chirality. Energy of π+σ plasmon is between 20 and 21 eV, and is insensitive to nanotube geometry. Dispersion of the π plasmon is mainly linear. Slope of dispersion curve increases with tube's translational period. © 2008 The American Physical Society.