Impact of graphene quantum capacitance on transport spectroscopy

摘要

We demonstrate experimentally that graphene quantum capacitance C_q can have a strong impact on transport spectroscopy through the interplay with nearby charge reservoirs. The effect is elucidated in a field-effect-gated epitaxial graphene device, in which interface states serve as charge reservoirs. The Fermi-level dependence of C_q is manifested as an unusual parabolic gate voltage (V_g) dependence of the carrier density, centered on the Dirac point. Consequently, in high magnetic fields B, the spectroscopy of longitudinal resistance (R_(xx)) vs V_g represents the structure of the unequally spaced relativistic graphene Landau levels (LLs). R_(xx) mapping vs V_g and B thus reveals the vital role of the zero-energy LL on the development of the anomalously wide v = 2 quantum Hall state.