We report on far infrared magneto-transmission measurements on a thin graphite sample prepared by exfoliation of highly oriented pyrolytic graphite. In magnetic field, absorption lines exhibiting a blue-shift proportional to sqrtB are observed. This is a fingerprint for massless Dirac holes at the H point in bulk graphite. The Fermi velocity is found to be c*=1.02x10^6 m/s and the pseudogap at the H point is estimated to be below 10 meV. Although the holes behave to a first approximation as a strictly 2D gas of Dirac fermions, the full 3D band structure has to be taken into account to explain all the observed spectral features.
@article{arxiv.0709.2681,
title = {Dirac fermions at the H point of graphite: Magneto-transmission studies},
author = {M. Orlita and C. Faugeras and G. Martinez and D. K. Maude and M. L. Sadowski and M. Potemski},
journal= {arXiv preprint arXiv:0709.2681},
year = {2009}
}