A many-body CPA study of quantum effects in the CMR manganites

Abstract A many-body coherent potential approximation (CPA) has been developed for simple models of the colossal magnetoresistance (CMR) manganites: the double-exchange (DE) and Holstein–DE models. In the classical limit for the local spins and phonons these models are one-electron problems and are exactly solvable within DMFT. The standard CPA, which is based on getting the atomic limit correct, is equivalent to DMFT for these one-electron problems. We are interested in the many-body case of quantum local spins and phonons in which DMFT must be solved numerically; our extended CPA offers an analytically tractable approximate solution of DMFT for this case. We use our CPA to discuss quantum effects on the electronic spectrum, Curie temperature and resistivity, comparing our results with experiment. Good semi-quantitative agreement is obtained for the temperature and field dependence of the resistivity.