  Orbital-lattice coupled excitation dynamics in orbitally degenerate
correlated systems are examined. We present a theoretical framework, where both
local vibronic excitations and superexchange-type inter-site interactions are
dealt with on an equal footing. We generalize the spin-wave approximation so as
to take local vibronic states into account. Present method is valid from weak
to strong Jahn-Teller coupling magnitudes. Two characteristic excitation modes
coexist; a low-energy dispersive mode and high-energy multi-peak mode. These
are identified as a collective vibronic mode, and Flanck-Condon excitations in
a single Jahn-Teller center modified by the inter-site interactions,
respectively. Present formalism covers vibronic dynamics in several
orbital-lattice coupled systems.
