Valley contrasting in epitaxial growth of In/Tl homoatomic monolayer with anomalous Nernst conductance

Over the past few years, various valleytronic properties have been predicted in graphene like p-electron honeycomb structures with staggered sublattice onsite potential; however, most of these studies are based on model calculations, and direct studies on real materials are still rare. In this paper, we propose an experimentally feasible structure based on an epitaxial growth of In/Tl honeycomb lattice on a semihydrogenated graphene/diamond thin film substrate. Our first-principles calculations reveal that due to different absorption sites of the two In/Tl sublattices, the inversion symmetry and quasi-two-dimensional inversion symmetry are broken, yielding inequivalent band gaps at the K and K′ points of the Brillouin zone. In addition, compared with previous graphene-based models, In/Tl also has a large spin-orbit coupling (SOC). In this regard, such a p-electron based system is a good candidate for valley selective circular polarization light absorption. Simultaneously, by integrating its Berry curvatures, we reveal a large SOC induced anomalous Nernst effect, which supports a pure spin current at its Fermi level.