Graphite from the viewpoint of Landau level spectroscopy: An effective graphene bilayer and monolayer

TL;DR

This study uses infrared spectroscopy to analyze bulk graphite under high magnetic fields, revealing that its electronic properties at the K point resemble a graphene bilayer with doubled inter-layer coupling, indicating massive Dirac fermions.

Contribution

It demonstrates that the optical response of bulk graphite at the K point mimics a graphene bilayer with an effective inter-layer coupling twice that of real bilayer graphene, providing new insights into graphite's electronic structure.

Findings

Identification of Landau level transitions at H and K points

K point electrons behave as massive Dirac fermions

Effective inter-layer coupling in graphite is twice that of graphene bilayer

Abstract

We describe an infrared transmission study of a thin layer of bulk graphite in magnetic fields up to B = 34 T. Two series of absorption lines whose energy scales as sqrtB and B are present in the spectra and identified as contributions of massless holes at the H point and massive electrons in the vicinity of the K point, respectively. We find that the optical response of the K point electrons corresponds, over a wide range of energy and magnetic field, to a graphene bilayer with an effective inter-layer coupling 2\gamma_1, twice the value for a real graphene bilayer, which reflects the crystal ordering of bulk graphite along the c-axis. The K point electrons thus behave as massive Dirac fermions with a mass enhanced twice in comparison to a true graphene bilayer.