Proximity-induced spin-orbit effects in graphene on Au

Abstract

We introduce a pz-d coupling model Hamiltonian for the π-graphene/Au bands that predicts a rather large intrinsic spin-orbit (SO) coupling as are being reported in recent experiments and DFT studies. Working within the analytical Slater-Koster tight-binding approach we were able to identify the overlapping orbitals of relevance in the enhancement of the SO coupling for both, the sublattice symmetric (BC), and the ATOP (AC) stacking configurations. Our model effective Hamiltonian reproduces quite well the experimental spectrum for the two registries, and in addition, its shows that the hollow site configuration (BC), in which the A/B sites remain symmetric, yields the larger increase of the SO coupling. We also explore the Au-diluted case keeping the BC configuration and showed that it renders the preservation of the SO-gap with a similar SO interaction enhancement as the undiluted case but with a smaller graphene-gold distance. arXiv:1910.01110v1 [cond-mat.mtrl-sci]

The Influence of Electronic Structure Modelling and Junction Structure on First-Principles Chiral Induced Spin Selectivity

“…This reinforces our earlier finding of SOC being inherited to a substantial degree from the electrodes for the Au-helix-Au system, 37 similar to proximity effects in graphene on gold. 133,134 In contrast, at least in photoemission experiments, a substantial spin polarization resulting from CISS is observed for light-element substrates just as much as for gold. To gain further insight into this phenomenon, we will study in tant carbon helix junction with 10-atom (6-3-1) metal clusters, using different metal atoms to build the electrodes (Cu, Ag, Au).…”

Ambipolar charge transport in quasi-free-standing monolayer graphene on SiC obtained by gold intercalation

“…However, if the phase-relaxation time is shorter than the spin-orbit scattering time τ SO > τ ϕ , the effects of spin-orbit scattering might not be observable in our samples under the measurement conditions (down to T = 2 K). In general, the SOI enhancement of MLG in proximity to Au is affected by the structure of graphene-Au interfaces including hybridization of orbitals, graphene-Au distances, and position of Au with respect to the graphene lattice [16,[34][35][36][37]. Band calculations predict that the optimal configuration for SOI enhancement is that of Au atoms located at hollow sites of graphene [16,34].…”

“…In general, the SOI enhancement of MLG in proximity to Au is affected by the structure of graphene-Au interfaces including hybridization of orbitals, graphene-Au distances, and position of Au with respect to the graphene lattice [16,[34][35][36][37]. Band calculations predict that the optimal configuration for SOI enhancement is that of Au atoms located at hollow sites of graphene [16,34]. Therefore, it is likely that the observation of positive magnetoconductance in our samples might be related to the Au atoms occupying random sites at the Bu-L/SiC interface.…”

The morphology of an intercalated Au layer with its effect on the Dirac point of graphene

“…Moreover, when positioning heavy metal atoms under graphene, the spin-orbit coupling will increase that causes band splitting 8 (e.g., of approximately 70 meV with an intercalated Au layer. This phenomenon comes from the breakage of a mirror symmetry due to interaction with the substrate [9][10][11][12] (which increases the Rashba splitting in graphene). A giant Rashba splitting is a very important property for a material to be used in the design of spintronic devices 13,14 .…”

“…A giant Rashba splitting is a very important property for a material to be used in the design of spintronic devices 13,14 . Perturbation theory has also earlier been used with the purpose to show that electrons within a p z orbital of graphene can be transferred to another p z orbital of graphene, either in pristine graphene or by using one of the d-orbitals, in the intercalated gold layer, as a bridge 9 .…”