Revealing the electronic structure of van der Waals antiferromagnetic NiPS₃ through synchrotron-based 𝜇-ARPES and alkali metal dosing

Antiferromagnetic NiPS₃ has recently emerged as a quantum material of considerable interest, thanks to the discovery of multiple new couplings involving electrons, spins, orbitals, phonons, and magnons. However, controversies and open questions persist concerning the fundamental origins of these couplings. A critical piece of information required to advance the understanding is the precise electronic band structure of NiPS₃. Angle-resolved photoemission spectroscopy (ARPES), combined with alkali metal dosing (AMD), can enable us to directly observe the subtle electronic states that appear around the Fermi surface, offering valuable insights into the intriguing quantum properties and interplays of the examined material. Here, we present a comprehensive characterization and analysis of the band structure of van der Waals layered antiferromagnet NiPS₃, leveraging state-of-the-art 𝜇-ARPES measurements supported by density functional theory (DFT) calculations. Theoretical DFT results identify the orbital contributions to the observed bands, providing a precise understanding of the experimental ARPES data. Crucially, AMD enables the observation of conduction band and defect-related states above the valence band maximum in NiPS₃. Furthermore, temperature dependent ARPES results across the Néel transition temperature of NiPS₃ reveal that the paramagnetic and antiferromagnetic phases have nearly identical band structures, underlining the highly localized character of Ni 𝑑 states. These findings substantially deepen our understanding of the electronic properties of NiPS₃ and lay a vital foundation for exploring the intriguing quantum phenomena it exhibits.