Self-energy approach to the correlated Kondo-lattice model

TL;DR

This paper introduces a self-energy method for the correlated Kondo-lattice model, incorporating electron-electron interactions via Hubbard terms, and provides insights into spectral properties and magnetic polaron formation across various regimes.

Contribution

It presents a novel interpolating self-energy approach that accurately captures the physics of the correlated Kondo-lattice model for all temperatures and couplings.

Findings

Spectral densities and densities of states are characterized.

Magnetic polarons are identified in the energy spectrum.

Spin exchange prevents full spin polarization even at strong couplings.

Abstract

We develop an interpolating self-energy approach to the correlated Kondo-lattice model. The correlation of the band electrons is taken into account by a Hubbard interaction. The method is based on a self-energy ansatz, the structure of which allows to fulfill a maximum number of exactly solvable limiting cases. The parameters of the ansatz are fitted to spectral moments via high-energy expansion of the self-energy. The band electron correlations are taken into account by an effective medium approach being correct in the strong coupling (U) regime. The theory is considered reliable for all temperatures, band occupations, and exchange couplings. Results are presented for the respective dependencies of spectral densities, quasiparticle densities of states, and characteristic correlation functions, and interpreted in terms of elementary spin exchange processes between itinerant conduction electrons and localized magnetic moments. The appearance of magnetic polarons, the typical quasiparticle of Kondo-lattices, in the energy spectrum is worked out. Spin exchange processes prevent a total spin polarization of the band electrons even for arbitrarily strong exchange couplings as long as the local moments are represented by quantum mechanical spins.