Correlation effects in a simplified bilayer two-orbital Hubbard model at half filling

Motivated by the discovery of high-temperature superconductivity in bilayer nickelate La3Ni2O7 under pressure, we investigate the ground-state phase diagram and correlation effects using determinant quantum Monte Carlo simulations in a simplified bilayer two-orbital Hubbard model at half filling. Our results reveal the emergence of a nonmagnetic weakly insulating phase at weak on-site Hubbard interactions, transitioning to an antiferromagnetic Mott insulating phase as the interaction strength exceeds a critical value U/tx1 approximate to 4.15. This phase transition is consistent with the 3D O(3) Heisenberg universality class. Additionally, we analyze dynamical properties such as the single-particle spectral function and dynamic spin structure factor. The pronounced interlayer correlation of d3z2-r2 orbitals results in a downward trend and an extended flatness in the gamma band, mirroring the angle-resolved photoemission spectroscopy findings under ambient pressure. Our numerical results provide important clues for understanding the strong correlation effects in La3Ni2O7.