Valley and Zeeman Splittings in Multilayer Epitaxial Graphene Revealed by Circular Polarization Resolved Magneto-infrared Spectroscopy

TL;DR

This study uses circular polarization magneto-infrared spectroscopy to investigate Landau level splittings in multilayer epitaxial graphene, revealing electron-hole asymmetry and valley/Zeeman effects with quantified g-factors.

Contribution

It provides detailed experimental insights into valley and Zeeman splittings in multilayer graphene, including effective g-factors, using polarization-resolved magneto-infrared spectroscopy.

Findings

Observation of Landau level transitions in multilayer graphene.

Identification of electron-hole asymmetry in the band structure.

Quantification of valley and Zeeman g-factors.

Abstract

Circular polarization resolved magneto-infrared studies of multilayer epitaxial graphene (MEG) are performed using tunable quantum cascade lasers in high magnetic fields up to 17.5 T. Landau level (LL) transitions in the monolayer and bilayer graphene inclusions of MEG are resolved, and considerable electron-hole asymmetry is observed in the extracted electronic band structure. For monolayer graphene, a four-fold splitting of the $n=0$ to $n=1$ LL transition is evidenced and attributed to the lifting of the valley and spin degeneracy of the zeroth LL and the broken electron-hole symmetry. The magnetic field dependence of the splitting further reveals its possible mechanisms. The best fit to experimental data yields effective $g$-factors, $g^*_{VS}=6.7$ and $g^*_{ZS}=4.8$, for the valley and Zeeman splitting, respectively.