Strong Superexchange in a $d^{9-{\delta}}$ Nickelate Revealed by Resonant Inelastic X-Ray Scattering

TL;DR

This study demonstrates that $d^{9-{ extdelta}}$ nickelates exhibit strong superexchange interactions, comparable to cuprates, which could be crucial for realizing high-temperature superconductivity in these materials.

Contribution

The paper provides experimental evidence of large superexchange in $d^{9-{ extdelta}}$ nickelates using resonant inelastic X-ray scattering, highlighting their potential for high-temperature superconductivity.

Findings

Magnon energy scale of ~80 meV observed

Nearest-neighbor magnetic exchange J = 69(4) meV measured

Nickelates show intermediate superexchange strength between cuprates and infinite-layer nickelates

Abstract

The discovery of superconductivity in a $d^{9-{\delta}}$ nickelate has inspired disparate theoretical perspectives regarding the essential physics of this class of materials. A key issue is the magnitude of the magnetic superexchange, which relates to whether cuprate-like high-temperature nickelate superconductivity could be realized. We address this question using Ni L-edge and O K-edge spectroscopy of the reduced trilayer nickelate $d^{9-1/3}$ La4Ni3O8 and associated theoretical modeling. A magnon energy scale of ~80 meV resulting from a nearest-neighbor magnetic exchange of $J = 69(4)4$ meV is observed, proving that $d^{9-{\delta}}$ nickelates can host a large superexchange. This value, along with that of the Ni-O hybridization estimated from our O K-edge data, implies that trilayer nickelates represent an intermediate case between the infinite-layer nickelates and the cuprates, and suggests that they represent a promising route towards higher-temperature nickelate superconductivity.