Valley to charge current conversion in graphene grain boundaries

TL;DR

This paper investigates how grain boundaries in graphene with Fermi velocity mismatch can convert valley polarization into charge current, advancing valleytronics by providing a theoretical framework for valley to charge current conversion.

Contribution

It generalizes the Dirac Hamiltonian model to include Fermi velocity gradients and derives boundary conditions, revealing how valley degeneracy breaking induces charge currents at grain boundaries.

Findings

Charge current is generated when valley degeneracy is broken.

Boundary conditions significantly influence scattering properties.

The work proposes a principle for valley to charge current conversion.

Abstract

The conduction properties of a grain boundary junction with Fermi velocity mismatch are analyzed. We provide a generalization of the Dirac Hamiltonian model taking into account the Fermi velocity gradient at the interface. General boundary conditions for the scattering problem are derived within the framework of the matching matrix method. We show that the scattering properties of the interface, as predicted by the theory, strongly depend on the boundary conditions used. We demonstrate that when the valley degeneracy is broken a charge current is established at the grain boundary interface. These findings provide the working principle of a valley to charge current converter, which is relevant for the emergent field of valleytronics.