Electronic structure of LaNi O3-x: An in situ soft x-ray photoemission and absorption study

We study the electronic structure of LaNi O3-x thin films using in situ soft x-ray photoemission and absorption spectroscopy. The in situ high-resolution measurements reveal that states at and near the Fermi level (EF) in the occupied and unoccupied densities of states are very sensitive to the oxygen content and are directly related to a metal-insulator transition. The highest quality epitaxial films of LaNi O3 show a temperature-dependent sharp peak at EF. A detailed analysis of its electrical resistivity confirms a T1.5 behavior over a large temperature range, which has been observed in earlier studies. Local density approximation band structure calculations indicate that the narrowing of the Ni d eg electron derived peak at EF cannot be reproduced by a strained crystal structure, suggesting a renormalization of electronic states at EF in LaNi O3. The T -dependent spectral changes at EF, coupled with the resistivity behavior and proximity to a metal-insulator transition, suggest the role of electron correlations in LaNi O3.