Low-energy properties of the Kondo lattice model

TL;DR

This paper investigates the zero-temperature properties of the Kondo lattice model using dynamical mean-field theory, revealing heavy Fermion behavior, Fermi surface evolution, and effects of electron-phonon coupling on the Kondo effect.

Contribution

It provides new insights into the phase diagram of the Kondo lattice model, including the impact of lattice degrees of freedom and electron-phonon interactions.

Findings

Evidence for a large Fermi surface in the paramagnetic phase.

Crossover from local-moment to heavy-fermion antiferromagnetism with increasing exchange.

Suppression of the Kondo effect and polaron formation at strong electron-phonon coupling.

Abstract

We study the zero-temperature properties of the Kondo lattice model within the dynamical mean-field theory. As impurity solver we use the numerical renormalization group. We present results for the paramagnetic case showing the anticipated heavy Fermion physics, including direct evidence for the appearance of a large Fermi surface for antiferromagnetic exchange interaction. Allowing for the formation of a Neel state, we observe at finite doping an antiferromagnetic metal below a critical exchange interaction, which shows a crossover from a local-moment antiferromagnet with a small Fermi surface for weak exchange coupling to a heavy-fermion antiferromagnet with a large Fermi surface for increasing exchange. Including lattice degrees of freedom via an additional Holstein term we observe a significant suppression of the Kondo effect, leading to strongly reduced lowenergy scale. For too large electron-phonon coupling we find a complete collaps of the heavy Fermi liquid and the formation of polarons.