Core-level x-ray photoemission and Raman spectroscopy studies on electronic structures in Mott-Hubbard type nickelate oxide NdNiO$_2$

TL;DR

This study uses X-ray photoemission and Raman spectroscopy to investigate the electronic structure and spin fluctuations in NdNiO$_2$, revealing its Mott-Hubbard nature and strong antiferromagnetic interactions.

Contribution

It provides experimental evidence confirming the Mott-Hubbard type electronic structure and quantifies spin fluctuations in NdNiO$_2$, supporting previous theoretical predictions.

Findings

NdNiO$_2$ has a large transfer energy.

NiO$_2$ planes are of Mott-Hubbard type.

Strong spin fluctuations with J=25 meV are observed.

Abstract

We perform core-level X-ray photoemission spectroscopy (XPS) and electronic Raman scattering studies of electronic structures and spin fluctuations in the bulk samples of the nickelate oxide NdNiO$_2$. According to Nd $3d$ and O $1s$ XPS spectra, we conclude that NdNiO$_2$ has a large transfer energy. From the analysis of the main line of the Ni $2p_{3/2}$ XPS, we confirm the NiO$_2$ planes in NdNiO$_2$ are of Mott-Hubbard type in the Zaanen-Sawatzky-Allen scheme. The two-magnon peak in the Raman scattering provides direct evidence for the strong spin-fluctuation in NdNiO$_2$. The peak position determines the antiferromagnetic exchange $J=25$~meV. Our experimental results agree well with our previous theoretical results.