Nontrivial spin structure of graphene on Pt(111) at the Fermi level due to spin-dependent hybridization

Abstract

The electronic and spin structure of a graphene monolayer synthesized on Pt(111) has been investigated experimentally by angle-and spin-resolved photoemission with different polarizations of incident synchrotron radiation and using density functional theory calculations. It is shown that despite the observed total quasifreestanding character of the dispersion of the graphene π state remarkable local distortions and breaks in the dispersions take place due to hybridization between the graphene π and Pt d states. Corresponding spin-dependent avoided-crossing effects lead to significant modification of the spin structure and cause an enhanced induced spin-orbit splitting of the graphene π states near the Fermi level in the region of theK point of the graphene Brillouin zone (BZ) with a magnitude of 80-200 meV depending on the direction in the BZ. Using p, s, and elliptical polarizations of the synchrotron radiation, the contributions of the graphene π and Pt d states were separated and their intersection at the Fermi level, which is important for effective spin injection between these states, was shown. Moreover, analysis of the data allows us to conclude that in the region of the Dirac point the spin structure of the system cannot be described by a Rashba splitting, and even a spin-orbit gap between lower and upper Dirac cones is observed.

Variation of the character of spin-orbit interaction by Pt intercalation underneath graphene on Ir(111)

“…Meanwhile, the Dirac point shifts approximately to 0.2 eV above the Fermi level. This value is in accordance with the Dirac point position for graphene on Pt(111) [20]. Moreover, one can see that after intercalation of a Pt monolayer in the region of BE of 0.1-0.3 eV additional states are visible, and local deviations from linear character of π state dispersion take place.…”

“…Moreover, it was shown [19] that the intercalation of 5d metals underneath graphene can also induce an appearance of the spin-orbit gap and topological insulator phase. Recently, we had observed similar effects in graphene on Pt(111) [20]. This system is characterized by a spin-dependent avoided-crossing effect between the Pt 5d and graphene π states directly at the Fermi level.…”

Hole doping, hybridization gaps, and electronic correlation in graphene on a platinum substrate

“…For example, a Raman spectroscopy study on the interface between graphene and Pt reports strongly suppressed Raman signals from graphene signifying strong interactions between them 9 , which can possibly cause Rashba-type spin splitting in graphene 10,11 . On the other hand, a recent experimental study on the electron band structure of graphene on a Pt(111) surface shows that overlying graphene exhibits typical characteristics of free-standing graphene 12,13 .…”

Monolayer charge-neutral graphene on platinum with extremely weak electron-phonon coupling

“…So far graphene on Pt(111) has been grown mostly by decomposing or dissolving hydrocarbon molecules [9][10][11][12][13][14] . These methods involve introducing a large amount (up to 0.05% 13 ) of external carbon source, and the dense nucleation sites often lead to graphene with multiple orientations and complicated Moiré superlattices 10,11 , suggesting significant graphenesubstrate interaction.…”