Dirac fermions at the H point of graphite: magnetotransmission studies.
We report on far infrared magnetotransmission measurements on a thin graphite sample prepared by exfoliation of highly oriented pyrolytic graphite. In a magnetic field, absorption lines exhibiting a blueshift proportional to sqrt[B] 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[over ] =( 1.02+/-0.02) x 10(6) m/s and the pseudogap |Delta| 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.
Grenoble High Magnetic Field Laboratory, CNRS, BP 166, F-38042 Grenoble Cedex 09, France. orlita@karlov.mff.cuni.cz
M
M
Orlita
C
C
Faugeras
G
G
Martinez
D K
DK
Maude
M L
ML
Sadowski
M
M
Potemski