Origin of spin current to charge current conversion in graphene on ferromagnet revealed by DFT with spin-orbit coupling calculations

Abstract

Spin current to charge current conversion (SCC) has been observed via spin-pumping experiments in single-layer graphene (SLG) on a ferromagnet primarily composed of Ni (SLG/Ni). A significant SCC is desired in spintronic materials for future device applications. The SCC in SLG/Ni was proposed to originate from the inverse Rashba Edelstein effect (IREE). However, previous angle-resolved photoemission spectroscopy (ARPES) measurements showed negligible Rashba splitting in the band dispersion along the direction, which does not support SCC via IREE. In this study, we employed first-principles calculations based on density functional theory with spin-orbit coupling (DFT+SOC). Our results confirm the absence of Rashba splitting along the direction, consistent with the ARPES data. However, we discovered significant Rashba splitting in the band dispersion along the Dirac point (K), providing the origin of SCC via IREE. The estimated SCC coefficients are of the same order of magnitude as those observed in spin-pumping experiments. Thus, this work reconciles the seemingly conflicting findings from spin-pumping and ARPES experiments and reveals the true magnetic origin of SCC via IREE in SLG on a ferromagnet. Plausible means and mechanisms on how to enhance the Rashba splitting will be discussed further in the meeting.