Strong interface-induced spin–orbit interaction in graphene on WS2

TLDR

Interfacial interactions can modify graphene’s electronic properties, as shown by satellite Dirac cones on hBN substrates. The study aims to extend such interfacial engineering to a wider class of materials to tailor electronic behavior. First‑principles calculations confirm that graphene on WS₂ experiences a strong spin–orbit interaction and yield a spin‑dependent low‑energy Hamiltonian. The enhanced spin–orbit coupling in graphene/WS₂ produces pronounced low‑temperature weak anti‑localization, reduces the spin‑relaxation time by two‑to‑three orders of magnitude compared with SiO₂ or hBN, makes it comparable to the intervalley scattering time, and indicates that WS₂ substrates could enable topological states in graphene.

Abstract

Interfacial interactions allow the electronic properties of graphene to be modified, as recently demonstrated by the appearance of satellite Dirac cones in the band structure of graphene on hexagonal boron nitride (hBN) substrates. Ongoing research strives to explore interfacial interactions in a broader class of materials in order to engineer targeted electronic properties. Here we show that at an interface with a tungsten disulfide (WS2) substrate, the strength of the spin-orbit interaction (SOI) in graphene is very strongly enhanced. The induced SOI leads to a pronounced low-temperature weak anti-localization (WAL) effect, from which we determine the spin-relaxation time. We find that spin-relaxation time in graphene is two-to-three orders of magnitude smaller on WS2 than on SiO2 or hBN, and that it is comparable to the intervalley scattering time. To interpret our findings we have performed first-principle electronic structure calculations, which both confirm that carriers in graphene-on-WS2 experience a strong SOI and allow us to extract a spin-dependent low-energy effective Hamiltonian. Our analysis further shows that the use of WS2 substrates opens a possible new route to access topological states of matter in graphene-based systems.