Magnetic phases in the correlated Kondo-lattice model

TL;DR

This paper investigates magnetic phases in an extended Kondo-lattice model with Coulomb interactions, revealing antiferromagnetic, ferromagnetic, and quantum critical behaviors through advanced numerical methods.

Contribution

It introduces a comprehensive analysis of magnetic ordering in the extended Kondo-lattice model using dynamical mean-field theory and NRG, highlighting new phase behaviors and quantum critical points.

Findings

Antiferromagnetic phase at half filling

Suppression of antiferromagnetism with doping and signs of phase separation

Emergence of ferromagnetism at large doping levels

Abstract

We study magnetic ordering of an extended Kondo-lattice model including an additional on-site Coulomb interaction between the itinerant states. The model is solved in the dynamical mean-field theory using Wilson's numerical renormalization group approach as impurity solver. For a bipartite lattice we find at half filling the expected antiferromagnetic phase. Upon doping this phase is gradually suppressed and hints towards phase separation are observed. For large doping the model exhibits ferromagnetism, the appearance of which can at first sight be explained by Rudermann-Kittel-Kasuya-Yosida interaction. However, for large values of the Kondo coupling $J$ significant differences to a simple Rudermann-Kittel-Kasuya-Yosida picture can be found. We furthermore observe signs of quantum critical points for antiferromagnetic Kondo coupling between the local spins and band states.