Distinct orbital contributions to electronic and magnetic structures in La 4 Ni 3 O 10

High- T c superconductivity has recently been discovered in Ruddlesden-Popper (RP)-phase nickelates under pressure, where the low-energy electronic structure is dominated by Ni d x 2 − y 2 and d z 2 orbitals. However, the respective roles of these orbitals in superconductivity remain unclear. Here, by combining x-ray absorption, electron energy loss spectroscopy, and density functional theory calculations on La 4 Ni 3 O 10 single crystals, we identify ligand holes in the p x , y orbitals of planar oxygen and the p z orbitals of apical oxygen, which hybridize with the Ni d x 2 − y 2 and d z 2 orbitals, respectively. These ligand holes enable orbital-selective O K -edge resonant inelastic x-ray scattering (RIXS) study, which reveals that d x 2 − y 2 states dominate the low-energy charge excitations and are more itinerant. We also observe an ∼ 0.1 eV bimagnon through RIXS and Raman spectroscopy. Our results reveal distinct contributions of Ni d x 2 − y 2 and d z 2 orbitals to the electronic and magnetic structure and provide direct experimental insights to understand the RP-phase nickelate superconductors.