Spin–Orbit Coupling Induced Gap in Graphene on Pt(111) with Intercalated Pb Monolayer

Abstract

Graphene is one of the most promising materials for nanoelectronics owing to its unique Dirac cone-like dispersion of the electronic state and high mobility of the charge carriers. However, to facilitate the implementation of the graphene-based devices, an essential change of its electronic structure, a creation of the band gap should controllably be done. Brought about by two fundamentally different mechanisms, a sublattice symmetry breaking or an induced strong spin-orbit interaction, the band gap appearance can drive graphene into a narrow-gap semiconductor or a 2D topological insulator phase, respectively, with both cases being technologically relevant. The later case, characterized by a spin-orbit gap between the valence and conduction bands, can give rise to the spin-polarized topologically protected edge states. Here, we study the effect of the spin-orbit interaction enhancement in graphene placed in contact with a lead monolayer. By means of angle-resolved photoemission spectroscopy, we show that intercalation of the Pb interlayer between the graphene sheet and the Pt(111) surface leads to formation of a gap of ∼200 meV at the Dirac point of graphene. Spin-resolved measurements confirm the splitting to be of a spin-orbit nature, and the measured near-gap spin structure resembles that of the quantum spin Hall state in graphene, proposed by Kane and Mele [ Phys. Rev. Lett. 2005 , 95 , 226801 ]. With a bandstructure tuned in this way, graphene acquires a functionality going beyond its intrinsic properties and becomes more attractive for possible spintronic applications.

Microscopic insight into the single step growth of in-plane heterostructures between graphene and hexagonal boron nitride

“…5c). This is the first time that the band dispersion in the valence band of graphene patches orientated with the main directions of the Pt(111) crystal has been measured, instead of the ARPES more usually reported, which pertains to the superstructure rotated by 30° [44,51,52,53] The full wave-vector ARPES data clearly prove the presence of graphene oriented with h-BN on a large scale, which occurs due to a 2D heteroepitaxial growth favoured by the h-BN edges [25,54].…”

Spin–orbit proximity effect in graphene on metallic substrates: decoration versus intercalation with metal adatoms

“…The first case should induce changes mainly in the G's properties already perturbed by the metal surface, while the latter might significantly alter the graphene-substrate proximity, as graphene will now interact with the metal mainly via the intercalated adatom. Importantly, both decoration and intercalation can be realized experimentally [12][13][14][15][16][17][18][19][20][21][22][23] and are known to provide several interesting options for engineering of graphene's properties, in addition to any possible enhancement of SOC [24]. Here, we will focus on two previously studied models, G/Pt(111) and G/Au/Ni(111) which present markedly different electronic and magnetic properties, and consider the adsorption of one species for each system, namely, a Pt adatom for G/Pt(111) and an Au adatom for G/Au/Ni(111).…”

Quasi-free-standing single-layer WS2 achieved by intercalation

“…It has even been shown that the stepwise intercalation of silicon and oxygen can lead to silicon oxide formation under epitaxial graphene, electrically isolating the graphene from the highly conductive substrate on which it is grown [27], and re-establishing the innate properties of the graphene. Further effects of intercalation can be the generation of substantial electron or hole doping densities [24,[28][29][30], an increase in the intrinsically very weak spin-orbit interaction [31,32] and the induction of superconductivity [33]. Given this ability to bestow graphene with new properties and to suppress the graphene-substrate interaction by intercalation, it is tempting to assume that epitaxially grown SL TMDCs could equally profit from such an approach.…”