Electrostatic Tuning of Bilayer Graphene Edge Modes

We study the effect of a local potential shift induced by a side electrode on the edge modes at the boundary between gapped and ungapped bilayer graphene. A potential shift close to the gapped-ungapped boundary causes the emergence of unprotected edge modes, propagating in both directions along the boundary. These counterpropagating edge modes allow edge backscattering, as opposed to the case of valley-momentum-locked edge modes. We then calculate the conductance of a bilayer graphene wire in presence of finger-gate electrodes, finding strong asymmetries with energy inversion and deviations from conductance quantization that can be understood with the gate-induced unprotected edge modes.

Automated summary

We investigate the impact of a local potential shift induced by a side electrode on the properties of the edge modes of bilayer graphene at the boundary between gapped and ungapped regions. It is found that a potential shift near the gapped-ungapped boundary leads to the emergence of unprotected edge modes that propagate in both directions along the boundary. These counterpropagating edge modes allow for edge backscattering, in contrast to the valley-momentum-locked edge modes. Additionally, we analyze the conductance of a bilayer graphene wire in the presence of finger-gate electrodes and observe strong asymmetries, energy inversion, and deviations from conductance quantization, which can be explained by the gate-induced unprotected edge modes.