Twist Angle Dependent Cyclotron Orbits in Twisted Bilayer Graphene Measured with Time Domain Terahertz Spectroscopy

The electronic properties of twisted bilayer graphene (TBG) have been shown to sensitively depend on the twist angle. Controlling the twist angle is capable of producing electronic states that greatly differ from those of monolayer graphene. Despite significant research interest in TBG the twist angle dependence of electronic properties hasn't been rigorously measured. Using time-domain terahertz (THz) spectroscopy, we measured the Faraday rotation on CVD-grown graphene which was then stacked to make different twist-angle bilayer samples. We model the observed THz spectrum with a Drude term describing free electron like motion and a lattice polarizability to determine the effective mass and scattering rate change from small to large twist angles.