Monte Carlo study of the one-orbital model for manganites in the CMR regime

The thermal phase transition in the one-orbital model for manganites with cooperative phonons and superexchange coupling is studied using Monte Carlo simulations. In the absence of on-site disorder, the model has a second order phase transition from a paramagnetic insulating phase to a ferromagnetic metallic phase in the CMR regime. The CMR effect is found to be associated with short-range charge and spin correlations in the insulating phase. This clearly shows that the CMR effect arises from the competition between the ferromagnetic and a charge-ordered competing states. Motivated by a recent STM experiment, we also studied the local density of states in this one-orbital model. We show how the experimental results can be understood within our model.