Orbital-driven electronic anisotropy in nickel phosphorous trisulfide

• Experimental and first principle calculations study of the electronic band structure asymmetry of the NiPS 3 van der Waals layered material • X-ray linear dichroism, Jahn-Teller distortions and Wannier functions • Linearly polarized ARPES and dipole matrix elements calculation Transition-metal phosphorus trichalcogenides are a class of van der Waals materials having the potential to transform a diverse range of fields, from electronics to energy storage. Among these, nickel phosphorous trisulphide (NiPS 3 ) is particularly interesting with its strongly correlated zig-zag antiferromagnetic insulating state below the Néel temperature, which is, of about 150 K. This study delves into the electronic properties of NiPS 3 above the transition temperature, using state-of-the-art synchrotron-based techniques, including x-ray absorption spectroscopy (XAS) combined with x-ray linear dichroism (XLD) and angle-resolved photoemission spectroscopy (ARPES), in order to probe the chemical state and the momentum-resolved band structure. The experimental results, corroborated by density functional theory (DFT) calculations, unveil orbital asymmetries linked to the crystallographic lattice and the orbital content of the electronic structure, which presents a nearly flat band close to the Fermi level. Moreover, the calculated dipole matrix elements reproduce well the polarization dependence observed in valence band ARPES. Our data reveal details on the electronic properties of NiPS 3 , which could lead to innovative solutions and applications in areas such as advanced computing, photo-electrochemical devices, and photodetectors.