Measurement and Control of Chiral Edge States in Graphene

By using a unique ring-shaped device based on h-BN sandwiched graphene with two electrostatic p-n junctions (pnJs) we have experimentally probed the interactions between integer quantum-Hall edge-states along the physical edges of graphene and at electrostatic edges defined by the pnJs. A first pnJ is used to decouple the edge-state of the energetically lowest Landau level (LL) from the others while a second pnJ senses the amount of interaction between the lowest LL and the rest. These multiple-pnJ measurements show that all edge-states interact strongly and equilibrate along the graphene physical edge while also confirming our previous results [1] that the lowest LL edge-state is decoupled from the other LL’s along the electostatic pnJ. By combining electrostatic and etched edges, chiral edge-states can be spatially separated at appropriate pnJs and then returned and mixed at physical boundaries. These results illustrate methods to manipulate chiral edge-states in graphene and are an advancement towards demonstrating the control of topologically protected chiral systems necessary for quantum logic operations.
[1] NN Klimov, et al., Phys. Rev B 92, 241301 (2015).