Interlayer pairing in bilayer nickelates

Abstract The discovery of T _c ~ 80 K superconductivity in pressurized La ₃ Ni ₂ O ₇ has launched a new platform to study high-temperature superconductivity. Using non-perturbative dynamic cluster approximation quantum Monte Carlo calculations, we characterize the magnetic and superconducting pairing behavior of a realistic bilayer two-orbital Hubbard-Hund model of this system that describes the relevant Ni e _g states with physically relevant interaction strengths. We find a leading s ^± superconducting instability in this model at a temperature T ~ 100 K close to the experimentally observed T _c . Analyzing the orbital and spatial structure of the effective pairing interaction giving rise to this state reveals that the interaction predominantly acts between local interlayer pairs of the $${d}_{3{z}²-{r}²}$$ orbital. By correlating the strength of the interaction with that of the magnetic spin fluctuations we show that it is driven by strong interlayer spin-fluctuations arising from the $${d}_{3{z}²-{r}²}$$ orbital. These results provide first-time non-perturbative evidence supporting the picture that a simple single-orbital bilayer Hubbard model for the Ni $${d}_{3{z}²-{r}²}$$ orbital provides an excellent low-energy effective description of the superconducting behavior of La ₃ Ni ₂ O ₇ .