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Register a new userLarge spin-orbit splitting of deep in-gap defect states of engineered sulfur vacancies in monolayer WS2
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Structural defects in 2D materials offer an effective way to engineer new material functionalities beyond conventional doping in semiconductors. Specifically, deep in-gap defect states of chalcogen vacancies have been associated with intriguing phenomena in monolayer transition metal dichalcogenides (TMDs). Here, we report the direct experimental correlation of the atomic and electronic structure of a sulfur vacancy in monolayer WS2 by a combination of CO-tip noncontact atomic force microscopy (nc-AFM) and scanning tunneling microscopy (STM). Sulfur vacancies, which are absent in as-grown samples, were deliberately created by annealing in vacuum. Two energetically narrow unoccupied defect states of the vacancy provide a unique fingerprint of this defect. Direct imaging of the defect orbitals by STM and state-of-the-art GW calculations reveal that the large splitting of 252 meV between these defect states is induced by spin-orbit coupling. The controllable incorporation and potential decoration of chalcogen vacancies provide a new route to tailor the optical, catalytic and magnetic properties of TMDs.
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Recently a paper of Klimovskikh et al. was published presenting experimental and theoretical analysis of the graphene/Pb/Pt(111) system. The authors investigate the crystallographic and electronic structure of this graphene-based system by means of LEED, ARPES, and spin-resolved PES of the graphene $pi$ states in the vicinity of the Dirac point of graphene. The authors of this paper demonstrate that an energy gap of approx. 200 meV is opened in the spectral function of graphene directly at the Dirac point of graphene and spin-splitting of 100 meV is detected for the upper part of the Dirac cone. On the basis of the spin-resolved photoelectron spectroscopy measurements of the region around the gap the authors claim that these splittings are of a spin-orbit nature and that the observed spin structure confirms the observation of the quantum spin Hall state in graphene, proposed in earlier theoretical works. Here we will show that careful systematic analysis of the experimental data presented in this manuscript is needed and their interpretation require more critical consideration for making such conclusions. Our analysis demonstrates that the proposed effects and interpretations are questionable and require further more careful experiments.
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