Synthetic topological phases in bilayer graphene via van der Waals proximity induced spin orbit coupling

Spin orbit coupling (SOC) forms the basis of time reversal invariant topological insulators. While graphene provided the first theoretical model for a topological insulator, the small intrinsic SOC in carbon make such phases unobservable. Here we engineer a synthetic topological insulator-like phase in bilayer graphene via proximity induced SOC from WSe2 in a van der Waals heterostructure. At zero magnetic field, we observe a new incompressible phase at charge neutrality due to proximity induced Ising-type SOC, having equal and opposite magnitude on each layer. Transport measurements show enhanced conductance within this new phase, which is rapidly suppressed by an in-plane magnetic field, consistent with modeling that suggests the new phase hosts spin filtered edge states and has a nearly quantized spin Hall conductance. Interestingly, spin is approximately conserved in this system despite large Rashba spin orbit coupling, whose effects are strongly suppressed in the spin-filtered edge states. Remarkably, electric field can be used to tune the system between the quantum spin Hall phase and a trivial insulator, permitting reconfigurable topological edge state circuits.