Dirac and Normal Fermions in Graphite and Graphene: Implications to the Quantum Hall Effect

TL;DR

This paper analyzes the quantum Hall effect in graphite and graphene, revealing the coexistence of normal and Dirac-like carriers, which explains recent observations of integer and semi-integer quantum Hall effects in these materials.

Contribution

It demonstrates that both normal and Dirac-like carriers coexist in graphite, providing insight into the quantum Hall phenomena observed in these materials.

Findings

Identification of normal and Dirac-like carriers in graphite

Observation of simultaneous integer and semi-integer QHE in HOPG

Spectral analysis linking carriers to Berry phases

Abstract

Spectral analysis of Shubnikov de Haas (SdH) oscillations of magnetoresistance and of Quantum Hall Effect (QHE) measured in quasi-2D highly oriented pyrolytic graphite (HOPG) [Phys. Rev. Lett. 90, 156402 (2003)] reveals two types of carriers: normal (massive) electrons with Berry phase 0 and Dirac-like (massless) holes with Berry phase pi. We demonstrate that recently reported integer- and semi-integer QHE for bi-layer and single-layer graphenes take place simultaneously in HOPG samples.