Hybrid 2D semimetal heterostructures of graphene and WTe2: Part 1

Only a small handful of all the known van der Waals materials are semimetals in the monolayer limit. Although graphene and WTe₂ are both semimetals, their properties are quite distinct. Graphene has a Dirac dispersion and is highly conductive, whereas monolayer WTe₂ exhibits a correlated topological gap at charge neutrality, superconductivity upon doping, and strong spin-orbit coupling. Combining these two materials into a heterostructure offers two potential advantages: first, the possibility of endowing graphene with a large proximity-induced spin-orbit coupling, and second, the possibility of controllably screening many-body interactions in WTe₂ by varying the doping of the proximate graphene sheet. The latter is especially useful, as the nature of the correlated insulating state and superconductivity in WTe₂ remain mysterious. In this study, we fabricate heterostructures in which monolayer WTe₂ is interfaced with either monolayer or bilayer graphene. By performing electrical transport measurements, we detect substantial charge transfer between the two materials resulting from their work function mismatch. By carefully tracking the evolution of the device resistance upon gating, we are further able to construct detailed band alignment models. With this basic understanding as a foundation, we will discuss efforts to extract the size of the gap at neutrality in WTe₂ as a function of graphene doping in the second part of this presentation.