The electronic structure of high-quality van der Waals NiPS 3 crystals was studied using near-edge x-ray absorption spectroscopy (NEXAFS) and resonant photoelectron spectroscopy (ResPES) in combination with density functional theory (DFT) approach.The experimental spectroscopic methods, being element specific, allow to discriminate between atomic contributions in the valence and conduction band density of states and give direct comparison with the results of DFT calculations. Analysis of the NEXAFS and ResPES data allows to identify the NiPS 3 material as a charge-transfer insulator.Obtained spectroscopic and theoretical data are very important for the consideration of possible correlated-electron phenomena in such transition-metal layered materials, where the interplay between different degrees of freedom for electrons defines their electronic properties, allowing to understand their optical and transport properties and to propose further possible applications in electronics, spintronics and catalysis.

A broad family of the nowadays studied low-dimensional systems, including 2D materials, demonstrate many fascinating properties, which however depend on the atomic composition as well as on the system dimensionality. Therefore, the studies of the electronic correlation effects in the new 2D materials is of paramount importance for the understanding of their transport, optical and catalytic properties. Here, by means of electron spectroscopy methods in combination with density functional theory calculations we investigate the electronic structure of a new layered van der Waals $$\hbox {FePX}_3$$ FePX 3 (X: S, Se) materials. Using systematic resonant photoelectron spectroscopy studies we observed strong resonant behavior for the peaks associated with the $$3d^{n-1}$$ 3 d n - 1 final state at low binding energies for these materials. Such observations clearly assign $$\hbox {FePX}_3$$ FePX 3 to the class of Mott–Hubbard type insulators for which the top of the valence band is formed by the hybrid Fe-S/Se electronic states. These observations are important for the deep understanding of this new class of materials and draw perspectives for their further applications in different application areas, like (opto)spintronics and catalysis.

The electronic structure of the alloyed transition-metal phosphorus trichalcogenide van der Waals Fe1–x Ni x PS3 compounds is studied using X-ray absorption spectroscopy and resonant photoelectron spectroscopy combined with intensive density functional theory calculations. Our systematic spectroscopic and theoretical data demonstrate the strong localization of the Fe- and Ni-ions-derived electronic states that leads to the description of the spectroscopic data as belonging simultaneously to Mott–Hubbard and charge-transfer insulators. These findings reveal Fe1–x Ni x PS3 as unique layered compounds with dual character of the insulating state, pointing to the importance of these results for the description and understanding of the functionality of this class of materials in different applications.

Presently a lot of efforts are devoted to the investigation of new two-dimensional magnetic materials, which are considered as promising for the realization of the future electronics and spintronics devices....

Large-scale high-quality van der Waals CoPS 3 single crystals are synthesized using a chemical vapor transport (CVT) method. The crystallographic structure and electronic properties of this layered material are systematically studied using different spectroscopic methods (XPS, NEXAFS, and resonant photoelectron spectroscopy) accompanied by density functional theory (DFT) calculations. All experimental and theoretical data allow assignment of this material to the class of mixed Mott−Hubbard/charge-transfer insulator with U dd ≅ Δ. All obtained results can enrich the information on the new class of van der Waals materials, transition metal phosphorus trichalcogenides, and help to further effectively exploit their electronic, optical, and transport properties, which are important for adopting this kind of materials into different application areas, such as spintronics and catalysis.