Fractional quantum Hall effect in graphite

Yakov Kopelevich
University of Campinas (UNICAMP), Brazil (visiting HP Labs)

Measurements of basal plane longitudinal ρ_b(B) and Hall ρ_H(B) resistivities were performed on highly oriented pyrolytic graphite samples in pulsed magnetic field up to B = 50 T applied perpendicular to graphene planes, and temperatures 1.5 K ≤ T ≤ 4.2 K [1]. At B > 30 T we observed a sign change in ρ_H(B) from electron- to hole-like. The measurements revealed also the enhancement in ρ_b(B) for B > 34 T (T = 1.8 K), presumably associated with the field-driven charge density wave or Wigner crystallization transition. Besides, well defined plateaus in ρ_H(B) were detected in the ultra-quantum limit revealing signatures of fractional quantum Hall effect in graphite. The obtained results provide evidence that graphite can be described as a stack of graphene bilayers that exhibit integer (filling factor ν ≥ 1) or fractional (ν < 1) quantum Hall states.

[1] Y. Kopelevich et al., Phys. Rev. Lett. 103, 116802 (2009)