Polaronic Aspects of the two-dimensional Ferromagnetic Kondo Model

The 2D ferromagnetic Kondo model with classical corespins is studied for a hole doping up to x = 0.125 via unbiased Monte Carlo (MC) simulations. A canonical algorithm for finite temperatures is developed. We show that with realistic parameters for the manganites and at low temperatures, the double-exchange mechanism does not lead to phase separation on a two-dimensional lattice but rather stabilizes individual ferromagnetic polarons. A detailed analysis of unbiased MC results reveals that the polarons can be treated as independent particles. It is found that a simple polaron model perfectly describes the physics of the FM Kondo model. The ferromagnetic polaron picture provides an obvious explanation for the pseudogap in the one-particle spectral function $A_k(\omega)$ observed in the FM Kondo model.