Giant Rashba splitting in graphene due to hybridization with gold

Abstract

Graphene in spintronics is predominantly considered for spin current leads of high performance due to weak intrinsic spin-orbit coupling of the graphene p electrons. Externally induced large spin-orbit coupling opens the possibility of using graphene in active elements of spintronic devices such as the Das-Datta spin field-effect transistor. Here we show that Au intercalation at the graphene-Ni interface creates a giant spin-orbit splitting (B100 meV) of the graphene Dirac cone up to the Fermi energy. Photoelectron spectroscopy reveals the hybridization with Au 5d states as the source for this giant splitting. An ab initio model of the system shows a Rashba-split spectrum around the Dirac point of graphene. A sharp graphene-Au interface at the equilibrium distance accounts for only B10 meV spin-orbit splitting and enhancement is due to the Au atoms in the hollow position that get closer to graphene and do not break the sublattice symmetry.

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

“…On the one hand, platinum is a heavy d metal promising an enhanced interatomic potential gradient that is necessary for enhanced spin orbit splitting in the graphene π states, which is assumed to be induced due to interaction with the Pt d states similar to the case of the contact of graphene with Au [10][11][12]. Moreover, in accordance with Refs.…”

“…In particular, in the graphene spin filter it is used as a passive element, only for effective transport of spin current injected between two ferromagnetic (FM) electrodes. Nevertheless, recent series of works [10][11][12] demonstrate that interaction of graphene with intercalated heavy d metals such as Au leads to an enhanced spin-orbit splitting of the graphene π states near the Fermi level in the region of theK point of the Brillouin zone (BZ). It was shown that this effect is mainly determined by the hybridization between the d states of Au and π states of graphene and corresponding spin-dependent avoided-crossing effects involving these states.…”

Transport Gap Opening and High On–Off Current Ratio in Trilayer Graphene with Self-Aligned Nanodomain Boundaries

“…Moreover, the FWHM=600 meV is three times larger than FWHM measured by ARPES for high-quality quasi-freestanding single layer graphene on hexagonal SiC, Ir or Au. [38][39][40] Such significantly enhanced broadening can be ascribed either to 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 8 geometric contributions from a minority of rotational variants distinct from the nanodomains rotated by ±13.5° from the <110> directions or to quantum scattering of quasiparticles on structural imperfections. Both origins of the broadening are associated with the large number of rotational NBs.…”

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

“…Although graphene due to a small atomic number of carbon atoms has an extremely low value of intrinsic SOI, it was recently shown, that an interaction with the substrate can induce spin-dependent effects in graphene [13][14][15]. Hybridization of the graphene and substrate d states leads to the spin splitting of the Dirac conelike π state, with the value of splitting up to 100 meV.…”

“…Thus, the authors of Refs. [13,14] attributed the spin splitting near the Dirac point to the Rashba effect. On the other hand, it has been theoretically predicted that spin-orbit coupling can induce a topological phase in graphene, similar to topological insulators [16].…”