Electronic properties of rhombohedral graphite

  • Servet Ozdemir

Student thesis: Phd


Rhombohedral graphite thin films, or ABC stacked multilayer graphene systems had been attracting a lot of theoretical interest due to their predicted extremely flat bands in the low energy limit which were in principle susceptible to various many body interactions such as magnetism and superconductivity. However, due to the competing Bernal hexagonal phase being more energetically favourable, experimental investigations into rhombohedral stacked graphite films had been limited. Despite the recent breakthrough in identification of rhombohedral domains in exfoliated graphite films, the electron transport investigation into rhombohedral graphite films were carried out up to tetra-layer systems. This thesis reports the first experiments that systematically characterises rhombohedral graphite films up to 50 layers encapsulated by high quality hBN crystals. We find that, at high temperatures (above 50K) conduction properties of rhombohedral graphite films are dominated by thermal activation across the bulk gap resembling an intrinsic semiconductor. At lower temperatures however, a semiconductor-metal transition manifests itself with conduction across the metallic surfaces dominating transport properties, thus enabling the electron transport investigation of low energy flat bands. Through Landau level spectroscopy, we find that low energy band structure undergoes a trigonal warping as well as a modified dispersion. The low energy bands become not as flat as originally predicted having a E = p2 dispersion with a Berry phase of NPi. We find that, on samples with 9-12 layer thickness, an interaction induced gap opens at the charge neutrality point accompanied by Berry curvature. Magnetic field characterisation of the gap as well as its hysteretic behaviour suggests possible magnetisation accompanied by the gap opening. We also find that, as predicted theoretically, above a finite displacement field which overcomes the screening ability of surface charges of rhombohedral graphite films, a band gap opens, with this gap opening being absent on samples with stacking faults. Lastly, we study the transport properties of bulk charges, demonstrating a thickness (bulk-carrier density) dependent cross-over from three dimensional weak-antilocalization to weak-localization. We also show that, there is a finite Lorentz force induced displacement field generation on rhombohedral graphite when an in-plane magnetic field is applied perpendicular to current.
Date of Award6 Jan 2021
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorKonstantin Novoselov (Supervisor) & Artem Mishchenko (Supervisor)


  • mesoscopic physics
  • ABC graphite
  • topological insulators
  • van der Waals heterostructures
  • quantum transport
  • graphene
  • rhombohedral graphite

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