Spin Dynamics near the Quantum Critical Point of Heavy-Fermions

TL;DR

This paper investigates the spin dynamics near the quantum critical point in heavy-fermion systems, revealing a two-component susceptibility and confirming a two-band model through experimental comparison.

Contribution

It introduces a perturbative approach to the dynamical spin susceptibility in heavy-fermion systems, highlighting a two-component behavior and validating a two-band model with experimental data.

Findings

Identification of a quasielastic peak and a q-dependent inelastic peak

Inelastic peak position approaches zero at the transition

Strong agreement with neutron scattering experiments

Abstract

The dynamical spin susceptibility is studied in the magnetically-disordered phase of heavy-Fermion systems near the antiferromagnetic quantum phase transition. In the framework of the $S=1/2$ Kondo lattice model, we introduce a perturbative expansion treating the spin and Kondo-like degrees of freedom on an equal footing. The general expression of the dynamical spin susceptibility that we derive presents a two-component behaviour: a quasielastic peak as in a Fermi liquid theory, and a strongly q-dependent inelastic peak typical of a non-Fermi liquid behaviour. Very strikingly, the position of the inelastic peak is found to be pushed to zero at the antiferromagnetic transition with a vanishing relaxation rate. The comparison has been quantitatively made with Inelastic Neutron Scattering (INS) experiments performed in $CeCu_{6}$ and $Ce_{1-x}La_{x}Ru_{2}Si_{2}$. The excellent agreement that we have found gives strong support to a two-band model with new prospects for the study of the quantum critical phenomena in the vicinity of the magnetic phase transition.