Landau Quantization in Graphene Monolayer, Bernal Bilayer, and Bernal Trilayer on Graphite Surface

TL;DR

This study uses scanning tunnelling microscopy and spectroscopy to identify and analyze Landau quantization in decoupled graphene layers on graphite, revealing distinct electronic properties of monolayer, bilayer, and trilayer graphene.

Contribution

It demonstrates the ability to distinguish different graphene layers on graphite and characterizes their Landau quantization and electronic spectra in high magnetic fields.

Findings

Decoupled graphene monolayer shows Landau quantization of massless Dirac fermions.

Decoupled Bernal bilayer exhibits Landau quantization of massive Dirac fermions with a substrate-induced band gap.

Decoupled Bernal trilayer hosts both massless and massive Dirac fermions, with a correlation between their Fermi velocity and effective mass.

Abstract

Electronic properties of surface areas decoupled from graphite are studied using scanning tunnelling microscopy and spectroscopy. We show that it is possible to identify decoupled graphene monolayer, Bernal bilayer, and Bernal trilayer on graphite surface according to their tunnelling spectra in high magnetic field. The decoupled monolayer and bilayer exhibit Landau quantization of massless and massive Dirac fermions, respectively. The substrate generates a sizable band gap, ~35 meV, in the Bernal bilayer, therefore, the eightfold degenerate Landau level at the charge neutrality point is split into two valley-polarized quartets polarized on each layer. In the decoupled Bernal trilayer, we find that both massless and massive Dirac fermions coexist and its low-energy band structure can be described quite well by taking into account only the nearest-neighbor intra- and interlayer hopping parameters. A strong correlation between the Fermi velocity of the massless Dirac fermions and the effective mass of the massive Dirac fermions is observed in the trilayer. Our result demonstrates that the surface of graphite provides a natural ideal platform to probe the electronic spectra of graphene layers.