Hubbard Subbands and Superconductivity in the Infinite-Layer Nickelate

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 coupled. Particularly in this latter regime, mapping to a one-band model gives significant spectral weight transfer between the Hubbard subbands. Finally, we show how the symmetry of superconducting phases depends on the interaction parameters and determine the regions of d-wave or s-wave symmetry.