Conductance as a function of temperature in the double-exchange model

We have used the Kubo formula to calculate the temperature dependence of the electrical conductance of the double-exchange Hamiltonian. We average the conductance over a statistical ensemble of clusters, which are obtained by performing Monte Carlo simulations on the classical spin orientation of the double-exchange Hamiltonian. We find that for electron concentrations bigger than 0.1. the system is metallic at all temperatures. In particular, there are not any peaks or changes in slope observed in the temperature dependence of the resistivity near the magnetic critical temperature. We conclude that the double-exchange model is not able to explain the metal-to-insulator transition which experimentally occurs at temperatures near the magnetic critical temperature. [S0163-1829(99)03406-2].