Electric Field Dependence of the Weak Anti-Localization of Bilayer Graphene Proximity Coupled to WSe₂.

As is the case for single layer graphene, the intrinsic spin-orbit coupling (SOC) in bilayer graphene is extremely weak, but it can be increased by orders of magnitude when the graphene is proximity coupled to transition metal dichalcogenides (TMDs). We investigated the electric field dependence of bilayer graphene/WSe₂ heterostructures, monitoring the change in the SOC through the weak anti-localization signature in our magnetoconductance measurements. In this study we chose to use thin exfoliated WSe₂ because it shows the largest induced SOC in graphene as compared to other TMDs [1]. With both top and back gates, we carried out magnetoconductance measurements at a fixed carrier density in the valence band under different electric fields. We observed a systematic increase in the induced SOC when the electric field is tuned from 0.2 V/nm to -0.5 V/nm. By comparing areas of the same bilayer graphene channel which are both uncovered and covered by WSe_2, we also examined the predicted electric field induced insulating behavior in these heterostructures due to the proximity coupling to WSe₂.
[1] B. Yang, et al. Phys. Rev. B 96, 0411409 (R) (2017)