Phonon softening phenomena of the Γ 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 us with a unified way to discuss the curvature effect and the electron-phonon interaction.
@article{arxiv.1004.5473,
title = {Kohn Anomaly in Raman Spectroscopy of Single Wall Carbon Nanotubes},
author = {K. Sasaki and H. Farhat and R. Saito and M. S. Dresselhaus},
journal= {arXiv preprint arXiv:1004.5473},
year = {2010}
}