Hund's metal physics: from SrNiO$_2$ to NdNiO$_2$

TL;DR

This study investigates the electronic structure of Nd$_{1-x}$Sr$_x$NiO$_2$, revealing Hund's metal behaviors and how doping affects charge occupancy, providing insights into its superconducting properties.

Contribution

It demonstrates that Nd$_{1-x}$Sr$_x$NiO$_2$ exhibits Hund's metal characteristics and shows how doping influences electronic structure, advancing understanding of nickelate superconductors.

Findings

Nd$_{1-x}$Sr$_x$NiO$_2$ is a multi-orbital Hund's metal.

Charge occupancy remains stable despite doping due to hybridization effects.

Results align with experimental RIXS measurements.

Abstract

We study the normal state electronic structure of the recently discovered infinite-layer nickelate superconductor, Nd$_{1-x}$Sr$_x$NiO$_2$. Using SrNiO$_2$ as a reference, we find that Nd$_{1-x}$Sr$_x$NiO$_2$ is a multi-orbital electronic system with characteristic Hund's metal behaviors, such as metallicity, the importance of high-spin configurations, tendency towards orbital differentiation, and the absence of magnetism in regimes which are ordered according to static mean-field theories. In addition, our DFT+DMFT calculations with exact double counting scheme show that despite large charge carrier doping from SrNiO$_2$ to LaNiO$_2$, the Ni-$3d$ total occupancy is barely changed due to the decreased hybridization with the occupied oxygen-2$p$ states, and increased hybridization with the unoccupied La-5$d$ states. Our results are in good agreement with the existing resonant inelastic x-ray scattering measurements and pave the way to understand the pairing mechanism of Nd$_{1-x}$Sr$_x$NiO$_2$.