Millikelvin de Haas–van Alphen and magnetotransport studies of graphite

Abstract

Recent studies of the electronic properties of graphite have produced conflicting results regarding the positions of the different carrier types within the Brillouin zone, and the possible presence of Dirac fermions. In this paper we report a comprehensive study of the de Haas--van Alphen, Shubnikov--de Haas, and Hall effects in a sample of highly orientated pyrolytic graphite, at temperatures in the range 30$ $mK to 4$ $K and magnetic fields up to 12$ $T. The transport measurements confirm the Brillouin-zone locations of the different carrier types assigned by Schroeder, Dresselhaus, and Javan, Phys. Rev. Lett. 20, 1292 (1968): electrons are at the $K$ point, and holes are near the $H$ points. We extract the cyclotron masses and scattering times for both carrier types from the temperature- and magnetic-field-dependences of the magneto-oscillations. Our results indicate that the holes experience stronger scattering and hence have lower mobility than the electrons. We utilize phase-frequency analysis and intercept analysis of the $1/B$ positions of magneto-oscillation extrema to identify the nature of the carriers in graphite, whether they are Dirac or normal (Schr\"odinger) fermions. These analyses indicate normal holes and electrons of indeterminate nature.