Chirality dependent frequency shift of radial breathing mode in metallic carbon nanotubes

Abstract

A phonon frequency shift of the radial breathing mode for metallic single wall carbon nanotubes is predicted as a function of Fermi energy. Armchair nanotubes do not show any frequency shift while zigzag nanotubes exhibit phonon softening, but this softening is not associated with the broadening. This chirality dependence originates from a curvature-induced energy gap and a special electron-phonon coupling mechanism for radial breathing modes. Because of the particle-hole symmetry, only the off-site deformation potential contributes to the frequency shift. On the other hand, the on-site potential contributes to the Raman intensity, and the radial breathing mode intensity is stronger than that of the $G$ band. The relationship between the chirality dependence of the frequency shift of the radial breathing mode and the $\Gamma$ point optical phonon frequency shift is discussed.

12 pages, 7 figures

References in corpus (5)

• Non-adiabatic Kohn-anomaly in a doped graphene monolayer
• Optical Phonons in Carbon Nanotubes: Kohn Anomalies, Peierls Distortions and Dynamic Effects
• Phonon Linewidths and Electron Phonon Coupling in Nanotubes
• Curvature induced optical phonon frequency shift in metallic carbon nanotubes
• Local density of states at zigzag edge of carbon nanotubes and graphene