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

TL;DR

This study investigates the phonon dispersion and Kohn anomaly near the K point in bilayer graphene using resonant Raman spectroscopy, revealing the significance of electron-phonon interactions.

Contribution

It provides experimental evidence of the Kohn anomaly in bilayer graphene and refines the electronic structure parameters through Raman analysis.

Findings

Observation of phonon softening near the K point

Evidence of the Kohn anomaly in bilayer graphene

Importance of electron-phonon interactions in phonon dispersion

Abstract

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.