Optical Hall effect measurement of coupled phonon mode - Landau level transitions in epitaxial graphene on silicon carbide

We report on mid-infrared (600 - 4000 cm^-1), refection-type optical-Hall effect measurements on epitaxial graphene grown on C-face silicon carbide and present Landau-level transition features detected at 1.5 K as a function of magnetic field up to 8 Tesla. The Landau- level transitions are detected in reflection configuration at oblique incidence for wavenumbers below, across and above the silicon carbide reststrahlen range. Small Landau-level transition features are enhanced across the silicon carbide reststrahlen range due to surface-guided wave coupling with the electronic Landau-level transitions in the graphene layer. We analyze the spectral and magnetic-field dependencies of the coupled resonances, and compare our findings with previously reported Landau-level transitions measured in transmission configuration [4,5,6]. Additional features resemble transitions previously assigned to bilayer inclusion [21], as well as graphite [15]. We discuss a model description to account for the electromagnetic polarizability of the graphene layers, and which is sufficient for quantitative model calculation of the optical-Hall effect data.