We have investigated change in the electronic structures of atomically controlled ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x\mathrm{Mn}{\mathrm{O}}_3$ (LSMO) thin films as a function of hole-doping levels $\left(x\right)$ in terms of in vacuo photoemission spectroscopy (PES) and x-ray absorption spectroscopy (XAS) measurements. The in vacuo PES measurements on a well-ordered surface of high-quality epitaxial LSMO thin films enable us to reveal their intrinsic electronic structures, especially the structure near the Fermi level $\left(E_F\right)$. We found that overall the features of the valence band as well as the core levels monotonically shifted toward lower binding energy as $x$ was increased, indicating the systematic chemical-potential shift of LSMO thin films with hole doping. The peak nearest to $E_F$ due to the $e_g$ orbital is also found to move toward $E_F$, while the peak intensity decreases with increasing $x$. The loss of spectral weight with $x$ in the occupied density of states was compensated by the simultaneous increment of the shoulder structure in O $1s$ XAS spectra, suggesting the existence of a pseudogap, that is, a lowering in spectral weight at $E_F$, for all metallic compositions. These results indicate that the simple rigid-band model does not describe the electronic structure near $E_F$ of LSMO, and that the spectral weight transfer from below to above $E_F$ across the gap dominates the spectral changes with $x$ in LSMO thin films.

• Received 11 June 2004

DOI:https://doi.org/10.1103/PhysRevB.71.155420