Spin and Magnetic Field Dependences of Quasiparticle Mass in Ferromagnetic State of Heavy Fermions

Abstract

Abstract. We investigate the mechanism underlying the suppression of heavy-fermion mass enhancement in the presence of a magnetic field. In the framework of statistically consistent Gutzwiller method (SGA) we study the periodic Anderson model in the strong correlation limit. The finite-U corrections are included systematically allowing to describe the coexistence of Kondo compensation effect and ferromagnetic ordering, as well as weak delocalization of the f-electrons. In particular, we observe that the resulting mass enhancement factor of spin-up electrons and that of spin-down are not equal in ferromagnetic phases and depend strongly on the applied field and the f-level occupancy. We predict that mass enhancement for the spin-up quasiparticles is larger then that of spin-down and both of them decrease in the applied magnetic field. We argue that above features, as well as a nonmonotonic variation of the quasiparticle effective masses observed in our model are in good agreement with earlier experimental measurements for CexLa1−xB6.

Heavy fermions in a high magnetic field

“…At a first glance, this behavior seems to be at odds with the existing modern theories, as all of them predict an increase of one of the spin-dependent masses and a decrease of the other one. However, very recently it was shown [140] that in ferromagnetic state of heavy fermion compounds, the application of sufficiently strong magnetic field leads to a full polarization of the system. Then both spin-up and spin-down masses decrease with increasing magnetic field.…”

On the strongly correlated quantum matter paradigm: magnetism–superconductivity redux

“…The role of f-f exchange is to stabilize antiferromagnetism. What is absolutely amazing is the total compensation of magnetic moments in both the superconducting and the Kondo insulating states [20]. We think that it is thus impossible to separate the existence and compensation of magnetic moments in this strong correlated system from the pairing aspect even though the critical temperature of superconducting transition is low, of the order of 1 K or even less.…”

“…We have developed a method of treating magnetism [18] and the pairing [19] on the same footing. We believe that no approach can be regarded as realistic until the phase diagram of the type depicted in figure 3 is constructed, with a proper sequence of phases as a function of, e.g., hybridization between the relevant 4f and uncorrelated electrons (such a sequence of phases has been reproduced successfully very recently, see [20]). We believe that the approach is based on the so-called Anderson-Kondo Hamiltonian in the strong-correlation limit [18], in which Kondo-type interaction, residual hybridization and the kinetic f-f exchange interaction, have all been included within a single unified scheme.…”