  The doping variation of charge and orbital dynamics in perovskite-type
Y1-xCaxVO3 (0<x<0.1) is investigated by measurements of the optical
conductivity and Raman scattering spectra in comparison with the
larger-bandwidth system La1-xSrxVO3. We also take into consideration the
magnitude of the GdFeO3-type orthorhombic lattice distortion, which is large
and small in Y1-xCaxVO3 and La1-xSrxVO3, respectively, and discuss its effect
on the evolution of charge dynamics. The optical conductivity spectra show that
the doped hole is well localized and forms the small polaron like state. The
hole dynamics in Y1-xCaxVO3 is nearly isotropic up to the doping level of the
orbital order-disorder transition, while that in La1-xSrxVO3 is anisotropic in
the lightly doped region due to the one-dimensional orbital exchange
interaction. The possible origin of the difference in the hole dynamics is
discussed in terms of the local lattice distortion, which is induced by the
formation of the small polaron like state and becomes more significant for the
reduced one-electron bandwidth. In addition, the optical Mott-gap excitation in
the nominally C-type spin and $G$-type orbital ordered phase is distinct from
that for La1-xSrxVO3 in its intensity and spectral shape. This suggests that
the orthorhombic lattice distortion enhances the modification of the spin and
orbital ordering from the pure C-type and G-type, respectively. The systematic
study of Raman scattering spectra has shown that the dynamic G-type spin and
C-type orbital correlation subsists at low temperatures in the doping induced
phase of the nominally C-type SO and G-type OO.
