Phonon anharmonicities in graphite and graphene

TL;DR

This study uses first-principles calculations to analyze how phonons in graphite and graphene behave at finite temperatures, revealing unique anharmonic effects and decay mechanisms relevant for thermal management.

Contribution

It provides the first detailed first-principles analysis of phonon linewidths, shifts, and lifetimes in graphite and graphene, highlighting electron-phonon interactions and anharmonic decay channels.

Findings

Graphite's E2g phonon linewidth decreases with temperature due to electron-phonon interactions.

In graphene, the A'1 mode at K has dominant anharmonic lifetimes and decay channels.

Strong coupling of the A'1 mode with acoustic phonons affects ballistic transport.

Abstract

We determine from first-principles the finite-temperature properties--linewidths, line shifts, and lifetimes--of the key vibrational modes that dominate inelastic losses in graphitic materials. In graphite, the phonon linewidth of the Raman-active E2g mode is found to decrease with temperature; such anomalous behavior is driven entirely by electron-phonon interactions, and does not appear in the nearly-degenerate infrared-active E1u mode. In graphene, the phonon anharmonic lifetimes and decay channels of the A'1 mode at K dominate over E2g at G and couple strongly with acoustic phonons, highlighting how ballistic transport in carbon-based interconnects requires careful engineering of phonon decays and thermalization.