Raman Linewidth Contributions from Four-Phonon and Electron-Phonon Interactions in Graphene

TL;DR

This study investigates the effects of four-phonon anharmonicity and electron-phonon interactions on Raman linewidths in graphene, successfully explaining temperature-dependent behaviors that previous models could not.

Contribution

It explicitly considers four-phonon anharmonicity, phonon renormalization, and electron-phonon coupling to accurately explain Raman linewidths in graphene.

Findings

Four-phonon scattering significantly increases linewidth with temperature.

Electron-phonon interaction effects reverse above a certain doping threshold.

The model aligns well with experimental Raman measurements across temperatures.

Abstract

The Raman peak position and linewidth provide insight into phonon anharmonicity and electron-phonon interactions (EPI) in materials. For monolayer graphene, prior first-principles calculations have yielded decreasing linewidth with increasing temperature, which is opposite to measurement results. Here, we explicitly consider four-phonon anharmonicity, phonon renormalization, and electron-phonon coupling, and find all to be important to successfully explain both the $G$ peak frequency shift and linewidths in our suspended graphene sample at a wide temperature range. Four-phonon scattering contributes a prominent linewidth that increases with temperature, while temperature dependence from EPI is found to be reversed above a doping threshold ($\hbar\omega_G/2$, with $\omega_G$ being the frequency of the $G$ phonon).