By using ultra-violet photoemission spectroscopy (UPS) and soft x-ray absorption spectroscopy (XAS), we have observed a systematic change of the spectral function around the Fermi level in the perovskite-type conductive 3d1 system, Ca1-xSrxVO3. When we decrease the Sr concentration (x) from 1 to 0 in Ca1-xSrxVO3, UPS and XAS intensities near the Fermi level decrease, and the reduced spectral weight is transferred to high energy part about 2 eV below and above Fermi level. The high energy features are thought to correspond to the remnants of lower and upper Hubbard bands, and the spectral weight within ∼1eV of Fermi level is assigned to the quasiparticle excitations or renormalized 3d-band. That is, the observed systematic spectral change indicates the opening of Mott-Hubbard gap.
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