凯发

In this talk we will present a novel device based on a split-gate geometry on bilayer graphene which allows to observe quantized conductance steps as well pinch-off resistances exceeding GOhms. Confined quantum devices in graphene require tunneling barriers to decouple the quantum dot from the source and drain leads. At the same time the tunneling barriers should not be too high because otherwise the currents will be too small to be measured. Most graphene quantum devices have been etched leading to localized states at the edges. As a consequence the barrier conductances are non-monotonic functions of the applied gate voltages which makes tuning the tunneling barriers difficult to impossibly. It has been recognized that vertical electric fields applied across bilayer graphene open a bandgap. Such bandgaps have been used to device quantum point contact-like structures but with limited success since they do not allow to smoothly pinch off the current. Here we present a graphite-back gated bilayer graphene encapsulated in BN layers equipped with a split top gate with an additional gate tuning only the density in the constriction itself.