Quantum Hall Transport across Monolayer-Bilayer Boundary in Graphene

Magnetotransport across monolayer-bilayer boundary on a graphene piece has been studied in the quantum Hall state. The edge channel transport in monolayer-bilayer junctions has been discussed based on the Landauer-Buttiker picture following p-n bipolar junctions of monolayer graphene. We considered two extreme cases of transmission from input edge channels to output channels at the junction, the maximum transmission model and the full-mixing model. They give different two-terminal conductance as a function of carrier filling. We measured the two-terminal conductance in monolayer-bilayer junction devices, and the measured conductance agreed better with the full-mixing model. This result suggests that edge channels of monolayer and bilayer regions are almost fully mixed up at the monolayer-bilayer boundary.