Induced spin-orbit coupling in twisted graphene-TMDC heterobilayers: Twistronics meets spintronics

Transport experiments in graphene deposited on monolayer transition metal dichalcogenide (TMDC) have demonstrated weak antilocalization, Shubnikov-de Haas oscillations, spin lifetime anisotropy, spin Hall effect and Rashba-Edelstein effect [1]. This suggests that spin-orbit coupling (SOC) in graphene is enhanced by the strong intrinsic SOC of the nearby TMDC layer. Setting up a theoretical model of the graphene-TMDC heterobilayer we are able to explain the origin and predict the interlayer twist angle dependence of the induced SOC [2]. We derive the induced valley Zeeman and Rashba type SOC in terms of the TMDC band structure parameters and interlayer tunneling matrix elements. We find that the strength of the induced SOC can be strongly tuned by the twist angle. Provided that the energy of the Dirac point is close to the TMDC conduction band, up to a tenfold increase of the valley Zeeman (at 18 degrees twist angle) and a fourfold increase of the Rashba type induced SOC can be achieved. Moreover, we have extended our model to the case of graphene encapsulated in two TMDC layers, where the induced SOC is also modulated by the additional twist angle.

[1] Avsar, et al., arXiv:1909.09188 (2019).
[2] David, Rakyta, Kormányos, and Burkard, Phys. Rev. B 100, 085412 (2019).