Polarization selection rules for inter-Landau level transitions in epitaxial graphene revealed by infrared optical Hall effect

TL;DR

This study investigates the polarization selection rules of inter-Landau level transitions in epitaxial graphene using infrared optical Hall effect measurements, revealing different behaviors in coupled and decoupled graphene layers.

Contribution

It uncovers the polarization selection rules governing inter-Landau level transitions in epitaxial graphene and explains their origin through coupling mechanisms with magneto-optic plasma oscillations.

Findings

Decoupled graphene layers follow polarization mixing selection rules.

Coupled graphene layers follow polarization preserving selection rules.

Transitions are influenced by coupling with charge carrier plasma oscillations.

Abstract

We report on polarization selection rules of inter-Landau level transitions using reflection-type optical Hall effect measurements from 600 to 4000 cm-1 on epitaxial graphene grown by thermal decomposition of silicon carbide. We observe symmetric and anti-symmetric signatures in our data due to polarization preserving and polarization mixing inter-Landau level transitions, respectively. From field-dependent measurements we identify that transitions in decoupled graphene mono-layers are governed by polarization mixing selection rules, whereas transitions in coupled graphene mono-layers are governed by polarization preserving selection rules. The selection rules may find explanation by different coupling mechanisms of inter-Landau level transitions with free charge carrier magneto-optic plasma oscillations.