Helical scattering and valleytronics in bilayer graphene

TL;DR

This paper introduces a mechanism in bilayer graphene that enables spatial separation of electrons based on their valley index through angularly asymmetric scattering at pseudospin interfaces, facilitating valley polarization detection.

Contribution

It presents a novel valley-dependent scattering mechanism in bilayer graphene that enables spatial valley separation and polarization control using electrostatic interfaces.

Findings

Electrons in different valleys are transmitted preferentially at distinct angles.

The effect occurs over a large energy range.

Potential for valleytronic device applications.

Abstract

We describe an angularly asymmetric interface-scattering mechanism which allows to spatially separate the electrons in the two low-energy valleys of bilayer graphene. The effect occurs at electrostatically defined interfaces separating regions of different pseudospin polarization, and is associated with the helical winding of the pseudospin vector across the interface, which breaks the reflection symmetry in each valley. Electrons are transmitted with a preferred direction of up to 60 degree over a large energetic range in one of the valleys, and down to -60 degree in the other. In a Y-junction geometry, this can be used to create and detect valley polarization.