Incoherent Charge Dynamics in Perovskite Manganese Oxides

A minimal model is proposed for the perovskite manganese oxides showing the strongly incoherent charge dynamics with a suppressed Drude weight in the ferromagnetic and metallic phase near the insulator. We investigate a generalized double-exchange model including three elements; the orbital degeneracy of $e_g$ conduction bands, the Coulomb interaction and fluctuating Jahn-Teller distortions. We demonstrate that Lancz$\ddot{\mathrm{o}}$s diagonalization calculations combined with Monte Carlo sampling of the largely fluctuating lattice distortions result in the optical conductivity which quantitatively accounts for the experimental indications. It is found that all the three elements are indispensable to understand the charge dynamics in these compounds.