Origin and enhancement of spin-current to charge-current conversion in graphene on ferromagnet from first-principles study

Spin-current to charge-current conversion (SCC) has been observed by spin-pumping experiment in single layer graphene (SLG) on ferromagnet composed mostly of Ni [1]. It was proposed that the SCC could be due to the inverse Rashba Edelstein effect (IREE). However, a prior angle-resolved photoemission spectroscopy (ARPES) of SLG on Ni shows a negligible Rashba splitting on band dispersions along Γ [2], unsupportive of the SCC by IREE. In this present work, we used first-principles method based on density functional theory with spin-orbit coupling and found that, there is no Rashba splitting on band dispersions along Γ confirming ARPES, however, there are considerable Rashba splittings in the band dispersions along the Dirac point, K, paving the way for SCC by IREE, confirming the spin-pumping experiment [3]. Estimates of SCC coefficient are within the order of magnitude of the experiment's. With the clarifications above, new graphene structures with significantly enhanced Rashba splittings are revealed.