  When graphene is placed on a monolayer of semiconducting transition metal
dichalcogenide (TMD) its band structure develops rich spin textures due to
proximity spin-orbital effects with interfacial breaking of inversion symmetry.
In this work, we show that the characteristic spin winding of low-energy states
in graphene on TMD monolayer enables current-driven spin polarization known as
the inverse spin galvanic effect (ISGE). By introducing a proper figure of
merit, we quantify the efficiency of charge-to-spin conversion and show it is
close to unity when the Fermi level approaches the spin minority band.
Remarkably, at high electronic density, even though sub-bands with opposite
spin helicities are occupied, the efficiency decays only algebraically. The
giant ISGE predicted for graphene on TMD monolayer is robust against disorder
and remains large at room temperature.
