Kondo breakdown transitions and phase-separation tendencies in valence-fluctuating heavy-fermion materials

TL;DR

This paper explores how Kondo breakdown transitions in heavy-fermion materials are influenced by valence fluctuations, revealing potential first-order transitions and phase separation tendencies that relate to experimental observations.

Contribution

It introduces a parton mean-field theory to study the interplay of Kondo breakdown and valence fluctuations, highlighting the possibility of first-order transitions and inhomogeneous states.

Findings

Valence fluctuations can induce first-order Kondo-breakdown transitions.

Phase separation tendencies emerge near Kondo-breakdown points.

Inclusion of Coulomb interactions suggests inhomogeneous states are likely.

Abstract

The breakdown of the lattice Kondo effect in local-moment metals can lead to non-trivial forms of quantum criticality and a variety of non-Fermi-liquid phases. Given indications that Kondo-breakdown transitions involve criticality not only in the spin but also in the charge sector, we investigate the interplay of Kondo breakdown and strong valence fluctuations in generalized Anderson lattice models. We employ a parton mean-field theory to describe the transitions between deconfined fractionalized Fermi liquids and various confined phases. We find that rapid valence changes near Kondo breakdown can render the quantum transition first order. This leads to phase-separation tendencies which, upon inclusion of longer-range Coulomb interactions, will produce intrinsically inhomogeneous states near Kondo-breakdown transitions. We connect our findings to unsolved aspects of experimental data.