Probing the Band Structure of the Strongly Correlated Antiferromagnet NiPS<sub>3</sub> across Its Phase Transition.

Pestka, Benjamin; Bhattacharyya, Biplab; Rybak, Miłosz; Strasdas, Jeff; Budniak, Adam K; Harchol, Adi; Liebmann, Marcus; Leuth, Niklas et al. · ACS Nano · 2025

basic_science · Level V

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Abstract

NiPS<sub>3</sub> is an exfoliable van der Waals intralayer antiferromagnet with a zigzag-type spin arrangement. It is distinct from other TMPS<sub>3</sub> (TM: transition metal) materials by optical excitations into a strongly correlated state that is tied to the magnetic properties. However, the related fundamental band structure across the antiferromagnetic phase transition has not been probed yet. Here, we use angular-resolved photoelectron spectroscopy with μm resolution in combination with DFT + U calculations for that purpose. We identify a characteristic band shift across the <i>T</i><sub>N</sub>. It is attributed to bands of mixed Ni and S character related to the superexchange interaction of the Ni 3t<sub>2g</sub> orbitals. Moreover, we find a structure above the valence band maximum with little angular dispersion that could not be reproduced by the calculations. The discrepancy suggests the influence of many-body interactions beyond the DFT + U approximations, in striking contrast to the results on MnPS<sub>3</sub> and FePS<sub>3</sub>, where these calculations were sufficient for an adequate description.