Probing cyclotron resonant signatures and the AC quantum Hall effect in monolayer and heterogeneous graphene multilayers through mid-infrared, magneto-optical, polarization-sensitive spectroscopy
Ellis, Chase Trevor
MetadataShow full item record
In 1947 Phillip Wallace introduced the fundamental electronic properties of a single layer of graphite, known as graphene. At that time, graphene was introduced as a theoretical tool that could be used to approximate the band structure of bulk 3D graphite. However, decades later theorists found that graphene had remarkable electronic properties of its own, including charge carriers that behave like massless, relativistic particles. Fifty years after graphene's initial theoretical introduction, the first experimental realization of graphene arrived. Leading to a myriad of experiments were able to confirm many of graphene's extraordinary properties. Today, graphene is a booming field of research, which is continually revealing new surprises and novel technologies. In this Dissertation Project we are mainly concerned with the electronic properties of heterogeneous, epitaxial, graphene multilayers that are formed by annealing Si out of carbon face terminated (C-face) 4H-SiC. Graphene layers grown by this method are of particular interest due to their large-area and high mobility, which can exceed 200,000 cm 2 i -1 s -1 . Moreover, the heterogeneous nature of C-face graphene samples allows us to simultaneously probe the electronic structure of many types of graphene within a single sample. In this study we reveal over 18 interband cyclotron resonances (CR) from a variety of graphene multilayers in our mid-infrared, magneto-optical, polarization-sensitive measurements that are performed in the polar Kerr geometry. Furthermore, we introduce a new technique that is capable of simplifying CR measurements on highly-heterogeneous samples; confirm three theories concerning the magneto-electronic structure of graphene; explore electron-hole band asymmetries; determine the optical effects of SiC the substrate. Interestingly, we find that the Fermi energy plays a major role in the production of large polarization changes that occur near CR. Also, we have discovered that the magnitude of CR Kerr features is nearly constant over the temperature range of 15–175 K. Combining these two effects enables the possibility of new, room-temperature, opto-electronic devices that can control the polarization of infrared light via an electrostatic gate. In addition, we also present preliminary results of Kerr angle measurements that are performed on electrostatically-gated, graphene monolayers grown by chemical vapor deposition. These measurements reveal step-like and plateau-like features in the MIR Kerr angle as a function of gate voltage. While theory predicts the existence of such features due to the AC quantum Hall effect that persists in the THz regime, these effects are expected to vanish for MIR frequencies that are an order of magnitude larger. Thus, these interesting results raise exciting questions for experiment and theory to explore in the future.