  The evolution of electron correlation in Sr$_{x}$Ca$_{1-x}$VO$_3$ has been
studied using a combination of bulk-sensitive resonant soft x-ray emission
spectroscopy (RXES), surface-sensitive photoemission spectroscopy (PES), and ab
initio band structure calculations. We show that the effect of electron
correlation is enhanced at the surface. Strong incoherent Hubbard subbands are
found to lie ~ 20% closer in energy to the coherent quasiparticle features in
surface-sensitive PES measurements compared with those from bulk-sensitive
RXES, and a ~ 10% narrowing of the overall bandwidth at the surface is also
observed.
