Spectral evidence for NiPS3 as a Mott-Hubbard insulator

TL;DR

This study uses advanced spectroscopy and theoretical modeling to demonstrate that NiPS3 is a Mott-Hubbard insulator, clarifying its electronic nature and resolving previous debates about its classification.

Contribution

The paper provides experimental evidence and theoretical analysis showing NiPS3 as a Mott-Hubbard insulator, contrasting earlier charge-transfer insulator interpretations.

Findings

NiPS3 is confirmed as a Mott-Hubbard insulator.

Spectroscopic evidence distinguishes surface and bulk properties.

Theoretical modeling supports experimental results.

Abstract

The layered van der Waals trichalcogenide NiPS3 has attracted widespread attention due to its unique optical, magnetic, and electronic properties. The complexity of NiPS3 itself, however, has also led to ongoing debates regarding its characteristics such as the existence of self-doped ligand holes. In this study, X-ray absorption spectroscopy and resonant inelastic X-ray scattering have been applied to investigate the electronic structure of NiPS3. With the aid of theoretical calculations using the charge-transfer multiplet model, we provide experimental evidence for NiPS3 being a Mott-Hubbard insulator rather than a charge-transfer insulator. Moreover, we explain why some previous XAS studies have concluded that NiPS3 is a charge-transfer insulator by comparing surface and bulk sensitive spectra.