Superconductivity in the Two-Orbital Hubbard Model of Infinite-Layer Nickelates

Abstract

The pairing symmetry in infinite-layer nickelate superconductors has been an intriguing problem under heated debates. In this work, we study a two-orbital Hubbard model with one strongly correlated $3d$ orbital and one more itinerant $5d$ orbital, by using an eight-site cellular dynamic mean field theory study. We establish a superconducting phase diagram with $d_{x^2-y^2}$, $s_{\pm }$ and $d+is$ wave pairing symmetries, based on which we clarify the roles of various relevant parameters including hybridization $V$, itinerant carrier density $⟨n_c⟩$ and interaction $U_c$. We show that the inclusion of a less correlated $5d$ band in general suppresses the $d_{x^2-y^2}$ wave pairing. We demonstrate that the $d+is$ wave is maximized when the $5d$ orbital has a large Coulomb repulsion with intermediate hybridization parameter. We perform fluctuation diagnostics to show that the driving force behind the $d_{x^2-y^2}$ wave is the intraband antiferromagnetic fluctuations in the $3d$ orbital, while for the $s_{\pm }$ wave, the pairing is mainly from the antiferromagnetic correlations residing on the local $3d$-$5d$ bond in real space.

8 pages, 5 figures