Polaronic aspects of the two-dimensional ferromagnetic Kondo model

Abstract

The two-dimensional ferromagnetic Kondo model with classical core spinsis studied via unbiased Monte Carlo simulations for a hole doping up tox = 12.5%. A canonical algorithm for finite temperatures is developed. We show that, with realisticparameters for the manganites and at low temperatures, the double-exchange mechanismdoes not lead to phase separation on a two-dimensional lattice but rather stabilizesindividual ferromagnetic polarons for this doping range. A detailed analysis of unbiasedMonte Carlo results reveals that the polarons can be treated as independent particles forthese hole concentrations. It is found that a simple polaron model describes the physics ofthe ferromagnetic Kondo model amazingly well. The ferromagnetic polaron pictureprovides an obvious explanation for the pseudogap in the one-particle spectral functionAk(ω) observed in the ferromagnetic Kondo model.