Hubbard subbands and superconductivity in the infinite-layer nickelate

TL;DR

This paper explores the electronic structure and superconductivity in infinite-layer nickelates using a two-band model, revealing regimes that resemble cuprates and highlighting potential pairing symmetries.

Contribution

It demonstrates how a two-orbital model can reproduce one-band Hubbard physics and Kondo regimes, and analyzes the effects of screening on electronic correlations and superconducting pairing.

Findings

Weak screening leads to cuprate-like behavior with electrons pushed out of the s-band.

Strong screening results in both bands being partly filled with weak coupling.

Superconducting phases may exhibit either d-wave or s-wave symmetry.

Abstract

An effective two-dimensional two-band model for infinite-layer nickelates consists of bands obtained from $d_{x^2-y^2}$ and $s$--like orbitals. We investigate whether it could be mapped onto a single-band Hubbard model and the filling of Hubbard bands. We find that both one-band physics and a Kondo-lattice regime emerge from the same two-orbital model, depending on the strength of electronic correlations and the filling of the itinerant $s$-band. Next we investigate one-particle excitations by changing the screening. First, for weak screening the strong correlations push electrons out of the $s$-band so that the undoped nickelate is similar to a cuprate. Second, for strong screening the $s$ and $d_{x^2-y^2}$ bands are both partly filled and weakly couple. Particularly in this latter regime mapping to a one-band model gives significant spectral weight transfer between the Hubbard subbands. Finally we point out that the superconducting phases may have either $d$-wave or $s$-wave symmetry.