Phys. Rev. Lett. 116, 166102 (2016)

Thanks to its exceptionally long spin diffusion lengths and relaxation times, graphene is an ideal material for spintronics. However, the intrinsic spin–orbit coupling, arising from the atomic number of carbon atoms, is considered to be too weak to drive a spin-to-charge conversion via the inverse spin Hall effect. The Rashba interaction in graphene-based heterostructures is considered a more efficient mechanism, leading to the so-called inverse Rashba–Edelstein effect. The current lack of systematic experimental studies has not yet allowed researchers to discriminate clearly between these two scenarios.

Now, Sergey Dushenko and colleagues from Osaka University, along with collaborators at other Japanese institutions, demonstrate that the spin-to-charge conversion in single-layer graphene is surprisingly dominated by the intrinsic spin–orbit coupling. Single-layer graphene was deposited on a thin-film substrate made of yttrium iron garnet. The magnetization precession of the low-damping ferrimagnetic insulator was driven by an external magnetic field and efficiently injected spin currents in graphene under conditions of ferromagnetic resonance — the so-called spin pumping effect. The spin-to-charge conversion was then monitored by varying the charge carrier type and density of graphene by means of electrolytic gating. According to the authors, the actual dependence of the charge current on the gate voltage clearly ruled out any role of the Rashba interaction in the process.