Low energy excitations in graphite: The role of dimensionality and lattice defects

TL;DR

This study uses high-resolution ARPES to explore how interlayer coupling and lattice defects influence the low energy electronic excitations in graphite, revealing band splitting, Dirac fermions, electron-phonon interactions, and defect-induced localized states.

Contribution

It provides the first ARPES evidence of band splitting, Dirac fermions, and electron-phonon interactions in graphite, highlighting the effects of dimensionality and lattice disorder.

Findings

Observation of π band splitting near K point

Detection of massless Dirac fermions and parabolic quasiparticles

Identification of electron-phonon interaction signatures

Abstract

In this paper, we present a high resolution angle resolved photoemission spectroscopy (ARPES) study of the electronic properties of graphite. We found that the nature of the low energy excitations in graphite is particularly sensitive to interlayer coupling as well as lattice disorder. As a consequence of the interlayer coupling, we observed for the first time the splitting of the $\pi$ bands by $\approx$ 0.7 eV near the Brillouin zone corner K. At low binding energy, we observed signatures of massless Dirac fermions with linear dispersion (as in the case of graphene), coexisting with quasiparticles characterized by parabolic dispersion and finite effective mass. We also report the first ARPES signatures of electron-phonon interaction in graphite: a kink in the dispersion and a sudden increase in the scattering rate. Moreover, the lattice disorder strongly affects the low energy excitations, giving rise to new localized states near the Fermi level. These results provide new insights on the unusual nature of the electronic and transport properties of graphite.