Circular-Polarization Dependent Cyclotron Resonance in Large-Area Graphene in Ultrahigh Magnetic Fields

TL;DR

This study investigates cyclotron resonance in large-area graphene under ultrahigh magnetic fields, revealing doping characteristics and Fermi energy shifts through polarization-dependent infrared spectroscopy.

Contribution

It demonstrates the use of ultrahigh magnetic fields and polarized IR radiation to analyze cyclotron resonance and doping in large-area graphene, including effects of thermal annealing.

Findings

Strong p-type doping in as-grown graphene

Fermi energy shifts near the Dirac point after annealing

Simultaneous electron and hole cyclotron resonance observed

Abstract

Using ultrahigh magnetic fields up to 170 T and polarized midinfrared radiation with tunable wavelengths from 9.22 to 10.67 um, we studied cyclotron resonance in large-area graphene grown by chemical vapor deposition. Circular-polarization dependent studies reveal strong p-type doping for as-grown graphene, and the dependence of the cyclotron resonance on radiation wavelength allows for a determination of the Fermi energy. Thermal annealing shifts the Fermi energy to near the Dirac point, resulting in the simultaneous appearance of hole and electron cyclotron resonance in the magnetic quantum limit, even though the sample is still p-type, due to graphene's linear dispersion and unique Landau level structure. These high-field studies therefore allow for a clear identification of cyclotron resonance features in large-area, low-mobility graphene samples.