Fermi-surface evolution across the magnetic phase transition in the Kondo lattice model

TL;DR

This paper investigates the evolution of the Fermi surface in the Kondo lattice model across magnetic phase transitions, revealing how Mott localization and magnetism interplay and how external magnetic fields can induce localization and metamagnetic transitions.

Contribution

The study provides a detailed phase diagram of the Kondo lattice model using an extended Gutzwiller approach, highlighting the conditions under which Mott localization and magnetic order occur and evolve.

Findings

Fermi surface changes discontinuously during Mott localization without nesting.

Continuous evolution of Fermi surface during transition to itinerant magnetism near nesting.

External magnetic field can induce Mott localization and trigger a metamagnetic transition.

Abstract

We derive, by means of an extended Gutzwiller wavefunction and within the Gutzwiller approximation, the phase diagram of the Kondo lattice model. We find that generically, namely in the absence of nesting, the model displays an $f$-electron Mott localization accompanied by a discontinuous change of the conduction electron Fermi surface as well as by magnetism. When the non interacting Fermi surface is close to nesting, the Mott localization disentangles from the onset of magnetism. First the paramagnetic heavy fermion metal turns continuously into an itinerant magnet - the Fermi surface evolves smoothly across the transition - and afterwards Mott localization intervenes with a discontinuous rearrangement of the Fermi surface. We find that the $f$-electron localization remains even if magnetism is prevented, and is still accompanied by a sharp transfer of spectral weigth at the Fermi energy within the Brillouin zone. We further show that the Mott localization can be also induced by an external magnetic field, in which case it occurs concomitantly with a metamagnetic transition.