Tunable spin-orbit Dirac points in van der Waals heterojunctions of 2D h-InBi with graphene

We present a first-principles investigation of two-dimensional heterostructures composed of hexagonal InBi (h-InBi) monolayers interfaced with graphene, aiming at exploring their electronic and topological properties. Structural optimization and stacking analysis reveal that interlayer geometry critically influences charge redistribution, work function alignment, and electrostatic potential gradients across the interface. Our calculations show consistent charge transfer from InBi to graphene, with stacking-dependent modulation of the surface potential and induced bandgaps in graphene layers. Band structure analysis, performed with and without spin-orbit coupling (SOC), confirms the preservation of topological band inversion in InBi, with SOC-induced gaps of ∼0.12–0.14 eV. Proximity effects also open tunable bandgaps in graphene, reaching up to 247 meV in bilayer configurations. Spin texture mapping reveals in-plane spin polarization with negligible out-of-plane components, consistent with semimetallic Dirac materials. These findings demonstrate that h-InBi/graphene heterostructures retain robust topological features while offering tunable electronic properties, positioning them as promising candidates for low-dissipation spintronic and quantum electronic applications.