The quantum ferromagnetic transition in a clean Kondo lattice is discontinuous

TL;DR

This paper demonstrates that the quantum ferromagnetic transition in a clean Kondo lattice is discontinuous (first order), correcting previous beliefs that it was continuous, aligning theory with experimental observations.

Contribution

The study reveals that the quantum phase transition in the ferromagnetic Kondo-lattice model is first order, challenging prior assumptions of a second order transition.

Findings

Quantum phase transition is first order in the absence of quenched disorder.

The first order nature aligns with experimental results in metallic ferromagnets.

Contradicts earlier theoretical descriptions of a continuous transition.

Abstract

The Kondo-lattice model, which couples a lattice of localized magnetic moments to conduction electrons, is often used to describe heavy-fermion systems. Because of the interplay between Kondo physics and magnetic order it displays very complex behavior and is notoriously hard to solve. The ferromagnetic Kondo-lattice model, with a ferromagnetic coupling between the local moments, describes a phase transition from a paramagnetic phase to a ferromagnetic one as a function of either temperature or the ferromagnetic local-moment coupling. At zero temperature, this is a quantum phase transition that has received considerable attention. It has been theoretically described to be continuous, or second order. Here we show that this belief is mistaken; in the absence of quenched disorder the quantum phase transition is first order, in agreement with experiments, as is the corresponding transition in other metallic ferromagnets.