  We investigate the evolution of a photoexcitation in correlated materials
over a wide range of time scales. The system studied is a one-dimensional model
of a manganite with correlated electron, spin, orbital, and lattice degrees of
freedom, which we relate to the three-dimensional material
Pr$_{1-x}$Ca$_{x}$MnO$_3$. The ground-state phases for the entire composition
range are determined and rationalized by a coarse-grained polaron model. At
half-doping a pattern of antiferromagnetically coupled Zener polarons is
realized. Using time-dependent density-matrix renormalization group (tDMRG), we
treat the electronic quantum dynamics following the excitation. The emergence
of quasiparticles is addressed, and the relaxation of the nonequilibrium
quasiparticle distribution is investigated via a linearized quantum-Boltzmann
equation. Our approach shows that the magnetic microstructure caused by the
Zener polarons leads to an increase of the relaxation times of the excitation.
