Observation of the Kohn anomaly near the K point of bilayer graphene

D. L. Mafra, L. M. Malard, S. K. Doorn, H. Htoon, J. Nilsson, A. H. Castro Neto, M. A. Pimenta

Published 2009-07-19Version 1

The dispersion of electrons and phonons near the K point of bilayer graphene was investigated in a resonant Raman study using different laser excitation energies in the near infrared and visible range. The electronic structure was analyzed within the tight-binding approximation, and the Slonczewski-Weiss-McClure (SWM) parameters were obtained from the analysis of the dispersive behavior of the Raman features. A softening of the phonon branches was observed near the K point, and results evidence the Kohn anomaly and the importance of considering electron-phonon and electron-electron interactions to correctly describe the phonon dispersion in graphene systems.