Quasiparticles in heavy-fermion systems with nearly integer valence

Abstract

The theory describing the electron mass enhancement in Kondo-lattice heavyfermion systems is presented. The description is based on the picture of a spin Fermi liquid of RVB type which strongly interacts with conduction electrons. It is shown that the electronspinon scattering results in large phase shifts for conduction electrons near the Fermi level which mimic the resonance renormalization but does not involve f-electron states. The results are compared with dHvA data for several Ce-based compounds.

Interplay between heavy fermions and crystal-field excitation in Kondo lattices: Low-temperature thermodynamics and inelastic neutron scattering spectra of CeNiSn

“…We have taken it to be linear in T within the low-T interval 0 < T < 10 K with the Sommerfeld coefficient γ e =18 mJ/mol K 2 . This means that the electron contribution to the heavy fermion density of states in good samples can be as large as ≈ 50 per cent in agreement with the theoretical predictions for the spin liquid state of the Kondo lattices [22]. It is seen from figure 12, that the theoretical curve describes quite well the temperature behavior of C/T = γ + bT at low temperture and gives the maximum of C/T at T = 6 K. The latter is observed for the more perfect samples [21] where the data for higher temperatures are available.…”

“…separated by small energy interval which was estimated as ≈ 4.4 meV in a point charge approximation for the crystal field. Indeed, the purely electrostatic approximation is crude enough, because the covalent and exchange corrections should be taken into account as it is seen from our equations (21) and (22). These corrections result in additional reduction of the CF splitting (see below), so one can be sure that the third CF level is high enough in energy (≈ 14.0 meV according to calculations of [4]), and the latter state is irrelevant to the low-energy excitation spectrum.…”

“…Its reduction in comparison with the value of 48.4 K given by indirect experiment of [4] is easily explained by the effects of covalent and exchange renormalization given by the terms B G c , B E c and B G ex in eqs. ( 21) and (22). It is obvious that the covalent repulsion B Γ c of the localized levels E Γ from the free conduction band states above the Fermi level (21,22) is governed by the value of hybridization matrix elements |V i kΓ | 2 .…”

“…( 21) and (22). It is obvious that the covalent repulsion B Γ c of the localized levels E Γ from the free conduction band states above the Fermi level (21,22) is governed by the value of hybridization matrix elements |V i kΓ | 2 . Since the Fermi surface of CeNiSn is dominated by the p-partial waves [19], the hybridization is largest for the j z = ±1/2 and j z = ±3/2 components of the f-states.…”

Ginzburg-Landau functional for nearly antiferromagnetic perfect and disordered Kondo lattices

“…The electrons in a layer of the width T K around Fermi level interact non-adiabatically with spin fermions at low T . As a result the giant Migdal effect arises 55 which results in strong electron mass enhancement. So, the heavy fermion state in accordance with this picture is a two-component Fermi liquid where the characteristic energies of charge subsystem (slow electrons with ǫ < T K ) and spin subsystem (spinons with ω ∼ T sl ) are nearly the same).…”