Spin-dependent electronic phenomena in heavily-doped monolayer graphene

The controlled manipulation of doping levels in graphene is crucial for advancing next-generation low-power electronics. Owing to its peculiar band structure, graphene's electronic functionalities can be easily tuned by electron doping, resulting in the bandgap openings, orbital hybridization, and induced spin-polarization. Here, we unveil the substantial doping of the graphene layer and the emergence of a significant bandgap by sandwiching a monolayer graphene, supported on ferromagnetic cobalt, between two europium layers. Our angleand spin-resolved photoemission spectroscopy experiments, accompanied by dedicated density functional theory calculations, demonstrate that single-spin electron pockets form as a result of the hybridization of the topmost europium majority bands with graphene, while hybridization gaps are induced in the graphene pi* bands by the Eu minority bands. Spin-resolved measurements further emphasize a single-spin dispersionless contribution proximal to the Fermi level, possibly arising from the coupling of single-spin polarized graphene bands to optical phonons. This work provides crucial insights into the phase diagram of heavily doped graphene, with significant potential for the design and development of novel 2D systems.