  Hole dynamics in spin and orbital ordered vanadates with perovskite structure
is investigated. A mobile hole coupled to the spin excitation (magnon) in the
spin G-type and orbital C-type (SG/OC) ordered phase, and that to the orbital
excitation (orbiton) in the spin C-type and orbital G-type (SC/OG) one are
formulated on an equal footing. The observed fragile character of the (SG/OC)
order is attributed to the orbiton softening caused by a reduction of the
taggered magnetic order parameter. It is proposed that the qualitatively
different hole dynamics in the two spin-orbital ordered phases in vanadates can
be probed by the optical spectra.
