Spin-orbit splitting in graphene on metallic substrates

Electronic structure, cohesive and magnetic properties of iridium oxide clusters adsorbed on graphene

In this study, we investigated and revealed the electronic properties, geometric structures and binding behavior of small (IrO)_n and [Formula: see text] (n = 1-5) clusters within first principles calculations based on the density functional theory. The electronic and magnetic properties of small nanoclusters displayed significant size dependency due to strong quantum confinement effect. Moreover we considered the binding and structural modification of the clusters on graphene surface as a substrate. The cohesive energy per atom of isolated clusters increased with size of the cluster n. This shows that the increase in coordination number results in a more stable nanocluster with increased number of saturated bonds. Pristine (IrO)_n and [Formula: see text] clusters presented different structural motives at equilibrium. The ground states of (IrO)_n and [Formula: see text] clusters considered in this study were all magnetic except for (IrO)₄, [Formula: see text] , and [Formula: see text] . HOMO-LUMO gap E_HLG values displayed large variations due to size of the cluster, hence bond saturation. The structural configurations of free standing nanoclusters are slightly modified, when adsorbed on graphene. The adsorption behavior of a cluster on graphene was improved by an applied electric field yielding larger binding energy and larger charger transfer. We observed that electronic and magnetic ground state of the clusters strongly depend on optimized structural configuration for both bare and adsorbed on graphene monolayer.

Controllable magnetic correlation between two impurities by spin-orbit coupling in graphene

Two magnetic impurities on the edge of a zigzag graphene nanoribbon strongly interact with each other via indirect coupling, which can be mediated by conducting carriers. By means of Quantum Monte Carlo (QMC) simulations, we find that the spin-orbit coupling λ and the chemical potential μ in system can be used to drive the transition of local-spin exchange from ferromagnetism to anti-ferromagnetism. Since the tunable ranges for λ and μ in graphene are experimentally reachable, we thus open the possibilities for its device application. The symmetry in spatial distribution is broken by the vertical and the transversal spin-spin correlations due to the effect of spin-orbit coupling, leading to the spatial anisotropy of spin exchange, which distinguish our findings from the case in normal Fermi liquid.

Spin-helical Dirac states in graphene induced by polar-substrate surfaces with giant spin-orbit interaction: a new platform for spintronics

Spintronics, or spin electronics, is aimed at efficient control and manipulation of spin degrees of freedom in electron systems. To comply with demands of nowaday spintronics, the studies of electron systems hosting giant spin-orbit-split electron states have become one of the most important problems providing us with a basis for desirable spintronics devices. In construction of such devices, it is also tempting to involve graphene, which has attracted great attention because of its unique and remarkable electronic properties and was recognized as a viable replacement for silicon in electronics. In this case, a challenging goal is to lift spin degeneracy of graphene Dirac states. Here, we propose a novel pathway to achieve this goal by means of coupling of graphene and polar-substrate surface states with giant Rashba-type spin-splitting. We theoretically demonstrate it by constructing the graphene@BiTeCl system, which appears to possess spin-helical graphene Dirac states caused by the strong interaction of Dirac and Rashba electrons. We anticipate that our findings will stimulate rapid growth in theoretical and experimental investigations of graphene Dirac states with real spin-momentum locking, which can revolutionize the graphene spintronics and become a reliable base for prospective spintronics applications.