Anderson lattice with explicit Kondo coupling: general features and the field-induced suppression of heavy-fermion state in ferromagnetic phase

TL;DR

This paper investigates the effects of magnetic fields on the heavy-fermion state in the Anderson-Kondo lattice model, revealing a field-induced transition from a locked heavy fermion state to a fully spin-polarized phase with reduced effective mass.

Contribution

It introduces an extended Gutzwiller approach to the periodic Anderson model, incorporating finite-U corrections and analyzing magnetic field effects on heavy-fermion states in ferromagnetic phases.

Findings

Identification of a locked heavy fermion state at large hybridization.

Observation of a metamagnetic transition under strong magnetic fields.

Reduction of effective mass by up to 20% in the fully polarized state.

Abstract

We apply the extended (statistically-consistent, SGA) Gutzwiller-type approach to the periodic Anderson model (PAM) in an applied magnetic field and in the strong correlation limit. The finite-U corrections are included systematically by transforming PAM into the form with Kondo-type interaction and residual hybridization, appearing both at the same time. This effective Hamiltonian represents the essence of \textit{Anderson-Kondo lattice model}. We show that in ferromagnetic phases the low-energy single-particle states are strongly affected by the presence of the applied magnetic field. We also find that for large values of hybridization strength the system enters the so-called \textit{locked heavy fermion state}. In this state the chemical potential lies in the majority-spin hybridization gap and as a consequence, the system evolution is insensitive to further increase of the applied field. However, for a sufficiently strong magnetic field, the system transforms from the locked state to the fully spin-polarized phase. This is accompanied by a metamagnetic transition, as well as by drastic reduction of the effective mass of quasiparticles. In particular, we observe a reduction of effective mass enhancement in the majority-spin subband by as much as 20% in the fully polarized state. The findings are consistent with experimental results for Ce$_x$La$_{1-x}$B$_6$ compounds. The mass enhancement for the spin-minority electrons may also diminish with the increasing field, unlike for the quasiparticles states in a single narrow band in the same limit of strong correlations.