Temperature Dependence of Phonon Energies and Lifetimes in Single- and Few-layered Graphene

TL;DR

This study investigates how temperature and layer number affect phonon energies and lifetimes in multi-layered graphene using molecular dynamics simulations, revealing layer-dependent effects and the influence of interlayer interactions.

Contribution

It provides new insights into the temperature and layer dependence of phonon properties in graphene, comparing different interlayer potentials and their impact on phonon lifetimes.

Findings

Layer number has little effect on intra-layer phonon energies.

Inter-layer modes are significantly affected by the number of layers.

Phonon lifetimes increase with the number of layers, influenced by interlayer coupling.

Abstract

In this work, we have studied the phonon properties of multi-layered graphene with the use of Molecular Dynamics (MD) simulations and the k-space Autocorrelation Sequence (k-VACS) method. We calculate the phonon dispersion curves, densities of states and lifetimes $\tau$ of few-layered graphene of 1-5 layers and graphite. $\Gamma$-point phonon energies and lifetimes are investigated for different temperatures ranging from 80 K to 1000 K. The study focuses on the impact of the interlayer interaction and temperature on the energies and lifetimes of the $\Gamma$-point phonons, as well as the type of interlayer potential used. For the later we used the Kolmogorov-Crespi (KC) and the Lennard-Jones (LJ) potentials. We have found that the number of layers $N$ has little effect on the intra-layer (ZO and G) mode energies and greater effect on the inter-layer (Layer Shearing and Layer Breathing) modes, while $\tau$ is generally affected by $N$ for all modes, except for the Layer Shear mode. The trend of $N$ on the lifetimes was also found to independent of the type of potential used. For the Raman-active G phonon, our calculations show that the lifetime increase with $N$ and that this increase is directly connected to the strength of the interlayer coupling and how this is modelled.