Cryogenic terahertz magneto-optical transport in bilayer and trilayer graphene on sapphire

We investigate terahertz (THz) magneto-optical (MO) properties of bilayer and trilayer graphene on sapphire at 80 K under magnetic fields up to 8 T. Using polarization-resolved THz time-domain spectroscopy, the complex longitudinal and transverse MO conductivities are extracted to determine the transport parameters via the Drude model. We find that the carrier density and the effective electron mass in bilayer and trilayer graphene depend weakly on the magnetic field, while the electronic relaxation time increases significantly with the magnetic field. These results indicate that cryogenic and polarization-resolved THz MO spectroscopy is well-suited for investigating carrier dynamics of few-layer graphene on a substrate.