Electronic structure of La$_{1-x}$Sr$_{x}$CoO$_{3}$ investigated from doping evolution of its soft x-ray spectra

Perovskite cobalt oxide LaCoO$_{3}$ attracted a lot of attention because of its spin state transition around 90K, the interpretation of which is still under debate. We performed soft X-ray absorption and emission experiments on La$_{1-x}$Sr$_{x}$CoO$_{3}$ at O-K edge and Co-L edge with various doping from x = 0 to x = 30. The doping evolution of the spectra can be understood as a result of introduction of holes at the top of valence band accompanied with a lowering of the Fermi level. The significant change of oxygen K edge spectra with doping indicates that the top of the valence band is largely of oxygen character, indicating strong Co 3d -- O 2p hybridization. The bottom of unoccupied band has a double peak feature indicating a splitting e$_{g}$ band. This split is the largest in the undoped sample and becomes smaller with doping. A gap of less than 1eV is observed from the excitation feature in the emission spectra and its change with doping again indicates a lower Fermi level in doped samples.