Renormalized spin wave excitations in the antiferromagnetic Heisenberg-Kondo model for heavy fermions

TL;DR

This paper develops a microscopic model to describe renormalized spin wave excitations in antiferromagnetic heavy fermion compounds, matching experimental neutron scattering data and elucidating the interplay of RKKY and Kondo interactions.

Contribution

It introduces a perturbative derivation of an effective Hamiltonian for magnons in the Heisenberg-Kondo model, linking microscopic parameters to experimental spin wave observations.

Findings

Good agreement with neutron scattering data for CeIn3

Model clarifies the influence of RKKY and Kondo couplings on magnons

Provides a framework for analyzing spin excitations in heavy fermion systems

Abstract

Recent inelastic neutron scattering experiments in CeIn3 and CePd2Si2 single crystals, measured spin wave excitations at low temperatures. These two heavy fermion compounds exhibit antiferromagnetic long-range order, but a strong competition between the Ruderman-Kittel-Kasuya-Yosida(RKKY) interaction and Kondo effect is evidenced by their nearly equal Neel and Kondo temperatures. Our aim is to show how magnons such as measured in the antiferromagnetic phase of these Ce compounds, can be described with a microscopic Heisenberg-Kondo model as introduced by J.R.Iglesias, C.Lacroix and B.Coqblin, used before for studies of the non-magnetic phase. The model includes the correlated Ce-4f electrons hybridized with the conduction band, and we consider competing RKKY (Heisenberg-like J_{H}) and Kondo (J_{K}) antiferromagnetic couplings. Carrying on a series of unitary transformations, we perturbatively derive a second-order effective Hamiltonian which, projected onto the antiferromagnetic electron ground state, describes the spin wave excitations, renormalized by their interaction with correlated itinerant electrons. We numerically study how the different parameters of the model influence the renormalization of the magnons, yielding useful information for the analysis of inelastic neutron scattering experiments in antiferromagnetic heavy fermion compounds. We also compare our results with available experimental data, finding good agreement with the spin wave measurements in cubic CeIn3.