Competing Incommensurate Spin Fluctuations and Magnetic Excitations in Infinite-Layer Nickelate Superconductors

TL;DR

This paper investigates the magnetic excitations in infinite-layer nickelate superconductors, revealing stripe instabilities and magnon spectra that resemble doped cuprates, providing insights into their inhomogeneous ground states and superconductivity mechanisms.

Contribution

The study introduces a quantum many-body Green's function approach to analyze magnetic properties and excitations in nickelates, highlighting their similarity to doped cuprates and explaining inhomogeneity.

Findings

Presence of magnetic stripe instabilities across LaNiO₂ phase diagram

Magnon spectrum matches RIXS experimental results

Magnetic properties resemble doped cuprates with inhomogeneous ground states

Abstract

The recently discovered infinite-layer nickelates show great promise in helping to disentangle the various cooperative mechanisms responsible for high-temperature superconductivity. However, lack of antiferromagnetic order in the pristine nickelates presents a challenge for connecting the physics of the cuprates and nickelates. Here, by using a quantum many-body Green's function-based approach to treat the electronic and magnetic structures, we unveil the presence of many two- and three-dimensional magnetic stripe instabilities that are shown to persist across the phase diagram of LaNiO$_2$. Our analysis indicates that the magnetic properties of the infinite-layer nickelates are closer to those of the doped cuprates which host inhomogeneous ground states rather than the undoped cuprates. The computed magnon spectrum in LaNiO$_2$ is found to contain an admixture of contributions from localized and itinerant carriers. The theoretically obtained magnon dispersion is in accord with the results of the corresponding RIXS experiments. Our study gives insight into the origin of inhomogeneity in the infinite-layer nickelates and their relationship with the cuprates.