Coherent Carrier Transport in Grpahene npn Junctions

Abstract

We report on coherent carrier transport in high quality dual-gate graphene encapsulated by hexagonal boron nitride. The graphene in-plane npn junction, which was realized by tuning the top and back gate voltages, showed a clear resistance oscillation due to the Fabry-Perot interference in the npn cavity. When a small magnetic field was applied, the oscillation phase was shifted by π, indicating the observation of the Klein tunneling at the pn interfaces. In high magnetic fields, the resistance across the npn junctions exhibited distinct oscillations, whose trajectories were well reproduced by the numerical calculation assuming the magnetic flux quantization in the insulating region between the co-propagating p and n quantum Hall edge channels. The results suggest the coherent interference of carriers at the graphene quantum Hall pn junction.