Electrostatic tuning of bilayer graphene edge modes

TL;DR

This paper investigates how local electrostatic potential shifts influence edge modes in bilayer graphene, revealing the emergence of unprotected, counterpropagating edge states that affect conductance properties.

Contribution

It demonstrates how side electrode-induced potential shifts can create unprotected edge modes in bilayer graphene, altering edge transport and conductance behavior.

Findings

Potential shifts induce unprotected edge modes

Counterpropagating modes enable backscattering

Conductance shows asymmetries and deviations from quantization

Abstract

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.