Multi-component magneto-optical conductivity of multilayer graphene on SiC

TL;DR

This study investigates the magneto-optical properties of multilayer graphene on SiC, revealing multiple spectral components, electron-hole coexistence, and velocity asymmetries, advancing understanding of its electronic structure.

Contribution

It provides detailed experimental analysis of multilayer graphene's magneto-optical conductivity, identifying multiple spectral features and quantifying electron-hole asymmetry and velocity variations.

Findings

Multiple spectral components identified, including cyclotron resonance and Landau level transitions.

Electron-hole asymmetry of about 2% in Fermi velocity within a layer.

Optical intensity of Landau level transitions is lower than theoretical predictions.

Abstract

Far-infrared diagonal and Hall conductivities of multilayer epitaxial graphene on the C-face of SiC were measured using magneto-optical absorption and Faraday rotation in magnetic fields up to 7 T and temperatures between 5 and 300 K. Multiple components are identified in the spectra, which include: (i) a quasi-classical cyclotron resonance (CR), originating from the highly doped graphene layer closest to SiC, (ii) transitions between low-index Landau levels (LLs), which stem from weakly doped layers and (iii) a broad optical absorption background. Electron and hole type LL transitions are optically distinguished and shown to coexist. An electron-hole asymmetry of the Fermi velocity of about 2% was found within one graphene layer, while the Fermi velocity varies by about 10% across the layers. The optical intensity of the LL transitions is several times smaller than what is theoretically expected for isolated graphene monolayers without electron-electron and electron-phonon interactions.