Revealing the Electronic Structure of van der Waals Antiferromagnetic NiPS$_3$ through Synchrotron-Based $\mu$-ARPES and Alkali Metal Dosing

TL;DR

This paper uses advanced ARPES techniques and DFT calculations to reveal the detailed electronic structure of NiPS$_3$, including the effects of alkali metal dosing and temperature, providing new insights into its band gap and magnetic states.

Contribution

It provides the first direct observation of conduction and defect bands in NiPS$_3$, accurately determines its band gap, and demonstrates the stability of its electronic structure across magnetic transitions.

Findings

Band gap of 1.3 eV determined from ARPES.

Observation of conduction and defect bands.

Paramagnetic and antiferromagnetic states show similar spectra.

Abstract

This study presents a comprehensive analysis of the band structure in NiPS$_3$, a van der Waals layered antiferromagnet, utilizing high-resolution synchrotron-based angle-resolved photoemission spectroscopy (ARPES) and corroborative density functional theory (DFT) calculations. By tuning the parameters of the light source, we obtained a very clear and wide energy range band structure of NiPS$_3$. Comparison with DFT calculations allows for the identification of the orbital character of the observed bands. Our DFT calculations perfectly match the experimental results, and no adaptations were made to the calculations based on the experimental outcomes. The appearance of novel electronic structure upon alkali metal dosing (AMD) were also obtained in this ARPES study. Above valence band maximum, structure of conduction bands and bands from defect states were firstly observed in NiPS$_3$. We provide the direct determination of the band gap of NiPS$_3$ as 1.3 eV from the band structure by AMD. In addition, detailed temperature dependent ARPES spectra were obtained across a range that spans both below and above the N\'eel transition temperature of NiPS$_3$. We found that the paramagnetic and antiferromagnetic states have almost identical spectra, indicating the highly localized nature of Ni $d$ states.