Engineering quantum anomalous/valley Hall states in graphene via metal-atom adsorption: Anab-initiostudy

Abstract

We systematically investigate the magnetic and electronic properties of graphene adsorbed with diluted 3d-transition and noble metal atoms using first principles calculation methods. We find that most transition metal atoms (i.e. Sc, Ti, V, Mn, Fe) favor the hollow adsorption site, and the interaction between magnetic adatoms and π-orbital of graphene induces sizable exchange field and Rashba spin-orbit coupling, which together open a nontrivial bulk gap near the Dirac K/K ′ (Γ) points in the 4 × 4 (3 × 3) supercell of graphene leading to the quantum-anomalous Hall effect. We also find that the noble metal atoms (i.e. Cu, Ag, Au) prefer the top adsorption site, and the dominant inequality of the AB sublattice potential opens another kind of nontrivial bulk gap exhibiting the quantum-valley Hall effect in the 4 × 4 supercell of graphene.

Tuning the magnetic moments in zigzag graphene nanoribbons: Effects of metal substrates

“…In Table II we list the electron loss of the ZGNR in all the systems in the ground state. We can see that the s metals with smaller DOS at the Fermi level might have larger total charge transfer, which is different from the case in the previous works 25,26 where the metal adatoms are adsorped on a pure graphene flake and the charge transfer between the metal and graphene can be taken as a term to estimate the hybridization. In our model, the mismatch of DOS and charge transfer possibly implies that some low-energy electrons come into play.…”

Flat bands with Berry curvature in multilayer graphene

“…Adatom deposition also introduces a superlattice potential. For the appropriate choice of (time reversal symmetry breaking) adatoms, the two valleys acquire the same sign of Berry curvature [33][34][35]. The rest of the analysis proceeds exactly as before, only now the Berry curvature has the same sign everywhere in the flat band, and thus does not cancel.…”

Giant spin Hall effect in graphene grown by chemical vapour deposition

“…Graphene is an ideal material, if methods, which do not require chemical functionalization, to enhance its weak spin-orbit coupling (SOC) are devised 5 . The recent predictions of proximity enhanced SOC in graphene decorated with metallic adatoms, where electrons tunnel from graphene to adatoms and back, thereby locally enhancing the SOC, open up a new path [6][7][8][9][10] . The proximity-induced SOC in graphene decorated with physisorbed metallic adatoms is unique and different from hydrogenated graphene.…”