We have measured soft x-ray photoemission and O $1s$ x-ray absorption spectra of ${\mathrm{Ca}}_{1-x}{\mathrm{Sr}}_x\mathrm{Ru}{\mathrm{O}}_3$ thin films prepared in situ. The coherent and incoherent parts have been identified in the bulk component of the photoemission spectra, and spectral weight transfer from the coherent to the incoherent part has been observed with decreasing $x$, namely, with increasing orthorhombic distortion. We propose that, while the Ru $4d$ one-electron bandwidth does not change with $x$, the distortion, and hence the splitting of the $t_{2g}$ band, effectively increases electron correlation strength. Although strong mass enhancement is found in the electronic specific heat data, the coherent part remains wide, suggesting enhanced band narrowing only in the vicinity of $E_F$.

• Received 27 December 2004

DOI:https://doi.org/10.1103/PhysRevB.72.060404