Capacitance of Graphene Bilayer as a Which-Layer Probe

The unique capabilities of capacitance measurements in bilayer graphene enable probing of layer-specific properties that are normally out of reach in transport measurements. Furthermore, capacitance measurements in the top-gate and penetration field geometries are sensitive to different physical quantities: the penetration field capacitance probes the two layers equally, whereas the top gate capacitance preferentially samples the near layer, resulting in the near-layer capacitance enhancement effect observed in recent top-gate capacitance measurements. We present a detailed theoretical description of this effect and show that capacitance can be used to determine the equilibrium layer polarization, a potentially useful tool in the study of broken symmetry states in graphene.