Fermi-liquid-to-polaron crossover. II. Double exchange and the physics of colossal magnetoresistance

Abstract

We use the dynamical mean-field method to study a model of electrons Jahn-Teller coupled to localized classical oscillators and ferromagnetically coupled to ‘‘core spins.’’ The model, we argue, contains the essential physics of the ‘‘colossal magnetoresistance’’ manganites ${\mathrm{Re}}_{1\mathrm{-}\mathit{x}}$ ${\mathit{A}}_{\mathit{x}}$ ${\mathrm{MnO}}_3$. We determine the different regimes of the model and present results for the temperature and frequency dependence of the conductivity, the electron spectral function, and the root-mean-square lattice parameter fluctuations. We compare our results to data and give a qualitative discussion of important physics not included in the calculation. Extensive use is made of results from a companion paper [Phys. Rev. B 54, 5389 (1996)]. © 1996 The American Physical Society.