Low-energy perspective of interacting electrons in the normal state of superconducting bilayer nickelate

Frank Lechermann; Steffen Bötzel; Ilya M. Eremin

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arXiv · 2503.12412

Low-energy perspective of interacting electrons in the normal state of superconducting bilayer nickelate

Frank Lechermann·Steffen Bötzel·Ilya M. Eremin

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Abstract

Developing a low-energy model is essential for understanding unconventional superconductivity in bilayer nickelate La$_3$Ni$_2$O$_7$. Here, we analyze distinct low-energy scenarios of the normal state by downfolding the ab-initio determined band structure and applying the mean-field regime of rotational-invariant slave-boson theory. We compare models based on the single-site two-orbital, the two-site four-orbital and a proposed minimal cluster (MC) picture. The latter builds up on three adapted orbitals located on the sites of the basic Ni-O-Ni cluster across the bilayer. Intriguing interplay between the Hund coupling $J_{\rm H}$ and the interlayer exchange $J_{\perp}$ is encountered in the multiorbital multi-site problem. While the tendency for interlayer Ni-$d_{z^2}$ singlet formation is pronounced, a complete localization remains hindered by the coupling to the Ni-$d_{x^2-y^2}$ orbitals. The correlation physics in the MC picture is peculiar with respect to the effective interorbital/site exchange.

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Frank Lechermann, Steffen Bötzel, Ilya M. Eremin. 2025-05-16. Low-energy perspective of interacting electrons in the normal state of superconducting bilayer nickelate. https://arxiv.org/abs/2503.12412

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