Core-Level X-Ray Spectroscopy of Infinite-Layer Nickelate: LDA+DMFT Study

TL;DR

This study uses LDA+DMFT to analyze core-level X-ray spectra of infinite-layer nickelates, revealing the role of self-doping in NdNiO$_2$ and highlighting differences with LaNiO$_2$.

Contribution

It provides a detailed theoretical investigation of core-level spectra in nickelates, clarifying the impact of self-doping and optimizing model parameters to match experimental data.

Findings

Self-doping from Nd 5d states prevents Mott-Hubbard gap formation in NdNiO$_2$.

LDA+DMFT calculations reveal differences between NdNiO$_2$ and LaNiO$_2$ spectra.

Optimal charge-transfer energy parameters are identified to match experimental spectra.

Abstract

Motivated by recent core-level x-ray photoemission spectroscopy (XPS), x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) experiments for the newly-discovered superconducting infinite-layer nickelate, we investigate the core-level spectra of the parent compounds NdNiO$_2$ and LaNiO$_2$ using the combination of local density approximation and dynamical mean-field theory (LDA+DMFT). Adjusting a charge-transfer energy to match the experimental spectra, we determine the optimal model parameters and discuss the nature of the NdNiO$_2$ ground state. We find that self-doping from the Nd 5$d$ states in the vicinity of the Fermi energy prohibits opening of Mott-Hubbard gap in NdNiO$_2$. The present Ni $L_3$ XAS and RIXS calculation for LaNiO$_2$ cannot explain the difference to NdNiO$_2$ spectra.