Antiferromagnetic metal to heavy-fermion metal quantum phase transition in the Kondo lattice model: A strong coupling approach

TL;DR

This paper investigates the quantum phase transition from an antiferromagnetic metal to a heavy fermion metal in the Kondo lattice model using a strong coupling approach, revealing a continuous Fermi surface change driven by spin fluctuation softening.

Contribution

It introduces a strong coupling method that diagonalizes the Kondo term, showing that Kondo hybridization remains relevant and that the transition is driven by spin fluctuation softening.

Findings

Kondo hybridization persists in the antiferromagnetic phase.

Fermi surface volume change is continuous across the transition.

Transition driven by softening of localized spin fluctuations.

Abstract

We study the quantum phase transition from an antiferromagnetic metal to a heavy fermion metal in the Kondo lattice model. Based on the strong coupling approach we {\it first} diagonalize the Kondo coupling term. Since this strong coupling approach makes the resulting Kondo term {\it relevant}, the Kondo hybridization persists even in the antiferromagnetic metal, indicating that fluctuations of Kondo singlets are not critical in the phase transition. We find that the quantum transition in our strong coupling approach results from {\it softening of antiferromagnetic spin fluctuations of localized spins}, driven by the Kondo interaction. Thus, the volume change of Fermi surface becomes continuous across the transition. ......