Valley Hall effect and nonlocal resistance in locally gapped graphene

Abstract

We report on the emergence of bulk, valley-polarized currents in graphene-based devices, driven by spatially varying regions of broken sublattice symmetry, and revealed by nonlocal resistance (RNL) fingerprints. By using a combination of quantum transport formalisms, giving access to bulk properties as well as multiterminal device responses, the presence of a nonuniform local band gap is shown to give rise to valley-dependent scattering and a finite Fermi-surface contribution to the valley Hall conductivity, related to characteristics of RNL. These features are robust against disorder and provide a plausible interpretation of controversial experiments in graphene/hexagonal boron nitride superlattices. Our findings suggest both an alternative mechanism for the generation of valley Hall effect in graphene and a route towards valley-dependent electron optics, by materials and device engineering. ; S.R.P. acknowledges funding from the Irish Research Council under the Laureate awards program. J.H.G. and S.R. acknowledge funding from the European Union Seventh Framework Programme under Grant No. 881603 (Graphene Flagship). ICN2 is funded by the CERCA Programme/Generalitat de Catalunya and supported by the Severo Ochoa programme (MINECO Grant. No. SEV-2017-0706). The Center for Nanostructured Graphene is sponsored by the Danish National Research Foundation, Project No. DNRF103. ; Peer reviewed