Phonon structures in the electronic density of states of graphene in magnetic field

TL;DR

This paper investigates how electron-phonon interactions influence the electronic density of states in graphene under magnetic fields, revealing new spectral features and comparing theoretical predictions with experimental data.

Contribution

The study introduces a detailed calculation of phonon effects on Landau levels in graphene, highlighting new phenomena like level shifting, broadening, and splitting due to electron-phonon coupling.

Findings

Evidence for a phonon mode near the optical E2g energy

Observation of Landau level shifts and splittings

Estimated electron-phonon coupling strength with λ ≈ 0.07

Abstract

Unlike in ordinary metals, in graphene, phonon structure can be seen in the quasiparticle electronic density of states, because the latter varies on the scale of the phonon energy. In a magnetic field, quantization into Landau levels creates even more significant variations. We calculate the density of states incorporating electron-phonon coupling in this case and find that the coupling has pronounced new effects: shifting and broadening of Landau levels, creation of new peaks, and splitting of any Landau levels falling near one of the new peaks. Comparing our calculations with a recent experiment, we find evidence for a phonon with energy similar to but somewhat greater than the optical $E_{2g}$ mode and a coupling corresponding to a mass enhancement parameter $\lambda \simeq 0.07$.