Infrared magneto-spectroscopy of graphite in tilted fields

The electronic structure of Bernal-stacked graphite subject to tilted magnetic fields has been investigated using infrared magneto-transmission experiments. With the increasing in-plane component of the magnetic field B, we observe significant broadening and partially also splitting of interband inter-Landau level transitions, which originate at the H point of the graphite Brillouin zone, where the charge carriers behave as massless Dirac fermions. The observed behavior is attributed to the lifting of the twofold degeneracy of Landau levels at the H point - a degeneracy which in graphite complements the standard spin and valley degeneracies typical of graphene.