Kohn anomaly in Raman spectroscopy of single wall carbon nanotubes

Phonon softening phenomena of the r point optical modes including the longitudinal optical mode, transverse optical mode and radial breathing mode in metallic single wall carbon nanotubes are reviewed from a theoretical point of view. The effect of the curvature-induced mini-energy gap on the phonon softening which depends on the Fermi energy and chirality of the nanotube is the main subject of this article. We adopt an effective-mass model with a deformation-induced gauge field which provides its with a unified way to discuss the curvature effect and the electron-phonon interaction. (C) 2010 Elsevier B.V. All rights reserved.