Valley current generation using biased bilayer graphene dots

TL;DR

This paper demonstrates that bilayer graphene quantum dots with tunable interlayer potentials can generate robust valley-dependent scattering and currents, advancing the development of valleytronic devices in two-dimensional materials.

Contribution

It introduces a practical method to induce valley-dependent scattering in bilayer graphene quantum dots via easily tunable interlayer potentials, enabling experimental exploration of valleytronics.

Findings

Valley-dependent scattering observed in bilayer graphene quantum dots.

Robust valley currents depend on dot size and mass strength.

Embedding a biased bilayer dot in graphene also produces valley splitting.

Abstract

Intrinsic and extrinsic valley Hall effects are predicted to emerge in graphene systems with uniform or spatially-varying mass terms. Extrinsic mechanisms, mediated by the valley-dependent scattering of electrons at the Fermi surface, can be directly linked to quantum transport simulations. This is a promising route towards more complete experimental investigation of valleytronic phenomena in graphene, but a major obstacle is the difficulty in applying the sublattice-dependent potentials required. Here we show that strongly valley-dependent scattering also emerges from bilayer graphene quantum dots, where the gap size can be easily modulated using the interlayer potentials in dual-gated devices. Robust valley-dependent scattering and concomitant valley currents are observed for a range of systems, and we investigate the role of dot size, mass strength and additional potential terms. Finally, we note that a strong valley splitting of electronic current also emerges when a biased bilayer dot is embedded in a single layer of graphene, but that the effect is less robust than for a bilayer host. Our findings suggest that bilayer graphene devices with custom mass profiles provide an excellent platform for future valleytronic exploration of two-dimensional materials.