Strong Superexchange in a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>d</mml:mi></mml:mrow><mml:mrow><mml:mn>9</mml:mn><mml:mo>−</mml:mo><mml:mi>δ</mml:mi></mml:mrow></mml:msup></mml:mrow></mml:math> Nickelate Revealed by Resonant Inelastic X-Ray Scattering
Jiaqi Lin, Pablo Villar Arribi, G. Fabbris, Antía S. Botana, D. Meyers, H. Miao, Yao Shen, D. G. Mazzone, Jiatai Feng, S. G. Chiuzbăian, Abhishek Nag, A. C. Walters, Mirian García‐Fernández, Ke‐Jin Zhou, Jonathan Pelliciari, Ignace Jarrige, J. W. Freeland, Junjie Zhang, J. F. Mitchell, Valentina Bisogni, Xuerong Liu, M. R. Norman, M. P. M. Dean
Abstract
The discovery of superconductivity in a d^{9-δ} 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 d^{9-1/3} trilayer nickelates R_{4}Ni_{3}O_{8} (where R=La, Pr) and associated theoretical modeling. A magnon energy scale of ∼80 meV resulting from a nearest-neighbor magnetic exchange of J=69(4) meV is observed, proving that d^{9-δ} 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. Layered nickelates thus provide a route to testing the relevance of superexchange to nickelate superconductivity.