Unconventional Landau levels in bulk graphite revealed by Raman spectroscopy

TL;DR

This study uses Raman spectroscopy to uncover unconventional Landau levels in bulk graphite, revealing similarities with graphene bilayers and providing insights into its electronic structure under magnetic fields.

Contribution

It demonstrates the presence of unconventional Landau levels in bulk graphite, linking its electronic properties to those of massive Dirac fermions similar to graphene bilayers.

Findings

Observation of Landau level transitions scaling linearly with magnetic field

Evidence of massive Dirac fermions with Berry's phase 2π in bulk graphite

Spectroscopic similarity between bulk graphite and graphene multilayers

Abstract

The electronic Raman scattering of bulk graphite at zero magnetic field reveals a structureless signal characteristic of a metal. For T<~100 K and B > 2 T, several peaks at energies scaling linearly with magnetic field were observed and ascribed to transitions from the lowest energy Landau level(s) (LL) to excited states belonging to the same ladder. The LLs are equally (unequally) spaced for high (low) quantum numbers, being surprisingly consistent with the LL sequence from massive Dirac Fermions (m* = 0.033(2) m_e) with Berry's phase 2\pi found in graphene bilayers. These results provide spectroscopic evidence that much of the unconventional physics recently revealed by graphene multilayers is also shared by bulk graphite.