Recent optical conductivity σ(ω) experiments have revealed an
anomalous spectral distribution in the ferromagnetic phase of the perovskite
system La1−xSrxMnO3. Using finite temperature diagonalization techniques
we investigate σ(ω) for a model that contains only the
eg-orbital degrees of freedom. Due to strong correlations the orbital model
appears as a generalized t-J model with anisotopic interactions and 3-site
hopping. In the orbital t-J model σ(ω) is characterized by a broad
incoherent spectrum with increasing intensity as temperature is lowered, and a
Drude peak with small weight, consistent with experiment. Our calculations for
two-dimensional systems, which may have some particular relevance for the
double-layer manganites, show that the scattering from orbital fluctuations can
explain the order of magnitude of the incoherent part of σ(ω) in
the low temperature ferromagnetic phase. Moreover orbital correlation functions
are studied and it is shown that x2-y2 orbital order is prefered in the
doped planar model at low temperature.Comment: Revtex, 14 pages, 14 figure