Polaronic Aspects of the two-dimensional Ferromagnetic Kondo Model

TL;DR

This study uses Monte Carlo simulations to show that in a 2D ferromagnetic Kondo model, ferromagnetic polarons form instead of phase separation, and a simple polaron model explains key spectral features.

Contribution

It demonstrates that ferromagnetic polarons are stable and can be modeled as independent particles, providing new insights into the physics of the FM Kondo model.

Findings

Polarons are stable and act as independent particles.

A simple polaron model accurately describes the system.

The model explains the pseudogap in the spectral function.

Abstract

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.