Valley filtering using electrostatic potentials in bilayer graphene

TL;DR

This paper demonstrates that electrostatic gating in bilayer graphene can be used to achieve highly efficient valley filtering by controlling electron transmission through a quantum point contact.

Contribution

It introduces a method to selectively filter electrons by valley using electrostatic potentials, a novel approach in bilayer graphene devices.

Findings

Valley filtering is achieved by inverting the bias on one side of the QPC.

Transmission steps are observed when biases are equal on both sides.

Inverted bias allows only electrons from one Dirac valley to pass.

Abstract

Propagation of an electron wave packet through a quantum point contact (QPC) defined by electrostatic gates in bilayer graphene is investigated. The gates provide a bias between the layers, in order to produce an energy gap. If the gates on both sides of the contact produce the same bias, steps in the electron transmission probability are observed, as in the usual QPC. However, if the bias is inverted on one of the sides of the QPC, only electrons belonging to one of the Dirac valleys are allowed to pass, which provides a very efficient valley filtering.