The dynamical conductance of graphene tunnelling structures

Abstract

The dynamical conductances of graphene tunnelling structures were numericallycalculated using the scattering matrix method with the interaction effect included in aphenomenological approach. The overall single-barrier dynamical conductanceis capacitative. Transmission resonances in the single-barrier structure lead todips in the capacitative imaginary part of the response. This is different fromthe ac responses of typical semiconductor nanostructures, where transmissionresonances usually lead to inductive peaks. The features of the dips depend on theFermi energy. When the Fermi energy is below half of the barrier height, the dipsare sharper. When the Fermi energy is higher than half of the barrier height,the dips are broader. Inductive behaviours can be observed in a double-barrierstructure due to the resonances formed by reflection between the two barriers.