Time-resolved Raman Spectroscopy of Optical Phonons in Graphite: Phonon Anharmonic Coupling and Anomalous Stiffening

TL;DR

This study uses time-resolved Raman spectroscopy to investigate the dynamics of optical phonons in graphite, revealing their decay lifetime, anharmonic coupling, and an unusual transient stiffening effect linked to electron-phonon interactions.

Contribution

It provides new insights into phonon behavior in graphite, including phonon lifetime measurements and the observation of transient phonon stiffening due to electron-phonon coupling changes.

Findings

Optical phonon lifetime of 2.2 ps in graphite

Transient phonon stiffening observed after excitation

Reduction in electron-phonon coupling at high electronic temperatures

Abstract

Time-resolved Raman spectroscopy has been applied to probe the anharmonic coupling and electron-phonon interaction of optical phonons in graphite. From the decay of the transient anti-Stokes scattering of the G-mode following ultrafast excitation, we measured a lifetime of 2.2+/-0.1ps for zone-center optical phonons. We also observed a transient stiffening of G-mode phonons, an effect attributed to the reduction of the electron-phonon coupling for high electronic temperatures.