Far-infrared magnetospectroscopy of the Landau-level structure in graphite

We present a study of the magnetoreflectivity of pyrolytic graphite in fields up to 8 T. Circularly polarized radiation at fixed laser frequencies in the energy range 3-16 meV was used. In addition to the usual intraband (cyclotron resonance) transitions, we observe transitions from the special central and leg electron levels first predicted by Dresselhaus. The field positions of the resonances are compared to those resulting from the detailed theoretical calculation of Nakao. Excellent agreement is obtained for the value of the trigonal warping parameter γ₃ equal to 0.315 ±{} 0.015 eV.