Exploring valley polarized transport in graphene bilayer flakes

Abstract

Valleytronics offers new routes to explore possible dual electronic responses related to the valley origin of the carriers. Graphene is known as an optimal material for devices based on valley-filter transport due to the double Dirac cones. Here we focus on understanding the role played by geometrical spatial details in the valley-dependent transport of bilayered graphene flakes, with long length, simulating nanoribbons. Flakes of different widths are considered at the stacking region. We also explore changing the valley transmission when a bias potential is applied. A tight-binding Hamiltonian is used to model the system, and the conductance is obtained by Landauer-Büttiker’s formalism and recursive Green’s function method. Our findings show that considering different bilayered graphene flake widths produces valley-polarized transmissions due to the presence of edge states. Furthermore, the corresponding energy range for which the valley filter occurs depends on the width asymmetries details. The theoretical analysis presented here indicates a potential route for valley-filter transmission scenarios of relatively easy engineering implementation.