  Spin-orbit coupling (SOC) in graphene can be greatly enhanced by proximity
coupling it to transition metal dichalcogenides (TMDs) such as WSe2. We find
that the strength of the acquired SOC in graphene depends on the stacking order
of the heterostructures when using hexagonal boron nitride (h-BN) as the
capping layer, i.e., SiO2/graphene/WSe2/h-BN exhibiting stronger SOC than
SiO2/WSe2/graphene/h-BN. We utilize photoluminescence (PL) as an indicator to
characterize the interaction between graphene and monolayer WSe2 grown by
chemical vapor deposition. We observe much stronger PL quenching in the
SiO2/graphene/WSe2/h-BN stack than in the SiO2/WSe2/graphene/h-BN stack, and
correspondingly a much larger weak antilocalization (WAL) effect or stronger
induced SOC in the former than in the latter. We attribute these two effects to
the interlayer distance between graphene and WSe2, which depends on whether
graphene is in immediate contact with h-BN. Our observations and hypothesis are
further supported by first-principles calculations which reveal a clear
difference in the interlayer distance between graphene and WSe2 in these two
stacks.
