Relaxation dynamics of the Kondo lattice model

TL;DR

This paper investigates the nonequilibrium relaxation dynamics of the Kondo lattice model, revealing how different perturbations affect the transition between local moment and heavy Fermi liquid states.

Contribution

It provides a detailed analysis of the relaxation processes in the Kondo lattice model using nonequilibrium dynamical mean field theory and non-crossing approximation, highlighting the effects of various perturbations.

Findings

Relaxation time increases near the transition to the heavy Fermi liquid.

Strong perturbations can quickly induce a local moment state from the heavy Fermi liquid.

Cooling leads to a two-stage relaxation with Kondo gap formation and slow approach to equilibrium.

Abstract

We study the relaxation properties of the Kondo lattice model using the nonequilibrium dynamical mean field formalism in combination with the non-crossing approximation. The system is driven out of equilibrium either by a magnetic field pulse which perturbs the local singlets, or by a sudden quench of the Kondo coupling. For relaxation processes close to thermal equilibrium (after a weak perturbation), the relaxation time increases substantially as one crosses from the local moment regime into the heavy Fermi liquid. A strong perturbation, which injects a large amount of energy, can rapidly transform the heavy Fermi liquid into a local moment state. Upon cooling, the heavy Fermi liquid reappears in a two-stage relaxation, where the first step opens the Kondo gap and the second step corresponds to a slow approach of the equilibrium state via a nonthermal pathway.