In situ photoemission study of LaNiO₃ thin films grown by pulsed laser deposition

We investigate the electronic structure of high-quality single-crystal LaNiO₃(LNO) thin films using in situ photoemission spectroscopy (PES) in order to reveal the intrinsic electronic structure of LNO. The O 1s X-ray absorption (XAS) spectrum, which have much deeper probing depth than that of PES measurement, is in good agreement with previous studies on polycrystalline LNO surfaces. The in situ valence band PES spectrum shows well-resolved Ni 3d-derived t_2g and e_g features, while earlier X-ray photoemission studies on polycrystals showed a single band peak. The narrow e_g-derived feature exhibits enhanced intensity compared to local density approximation band structure calculations. The results are consistent with a renormalization of electronic states at E_F, in terms of the known enhanced effective mass.