We demonstrate experimentally that graphene quantum capacitance$C_{\mathrm{q}}$ can have a strong impact on transport spectroscopy through theinterplay with nearby charge reservoirs. The effect is elucidated in afield-effect-gated epitaxial graphene device, in which interface states serveas charge reservoirs. The Fermi-level dependence of $C_{\mathrm{q}}$ ismanifested as an unusual parabolic gate voltage ($V_{\mathrm{g}}$) dependenceof the carrier density, centered on the Dirac point. Consequently, in highmagnetic fields $B$, the spectroscopy of longitudinal resistance ($R_{xx}$) vs.$V_{\mathrm{g}}$ represents the structure of the unequally spaced relativisticgraphene Landau levels (LLs). $R_{xx}$ mapping vs. $V_{\mathrm{g}}$ and $B$thus reveals the vital role of the zero-energy LL on the development of theanomalously wide $\nu=2$ quantum Hall state.
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机译：我们通过实验证明，石墨烯量子电容$ C _ {\ mathrm {q}} $可以通过与附近电荷库的相互作用对传输光谱产生强烈影响。在场效应门控外延石墨烯器件中阐明了该效应，在该器件中，界面态充当电荷储存器。 $ C _ {\ mathrm {q}} $的费米能级依赖性表现为载流子密度的不寻常抛物线栅极电压（$ V _ {\ mathrm {g}} $）依赖性，其中心是狄拉克点。因此，在高磁场$ B $中，纵向电阻（$ R_ {xx} $）与$ V _ {\ mathrm {g}} $的光谱表示不等间距相对论石墨烯朗道能级（LLs）的结构。 $ R_ {xx} $相对于$ V _ {\ mathrm {g}} $和$ B $的映射揭示了零能LL在异常宽的$ nu = 2 $量子霍尔态的发展中的重要作用。
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