Magnetic Field-Induced Anomalies and Kondo Effect in Lanthanide in Heavy-Electron Systems

Abstract

We investigate the influence of magnetic fields on the heavy quasiparticles in the Kondo lattice system YbRh 2 Si 2 and in filled skutterudites containing Pr ions. In the Kramers system YbRh 2 Si 2 the Kondo singlets break up in an applied field which leads to a general reduction of the effective mass. The observed anomalous behavior of the specific heat is quantitatively described by the Renormalized Band method where the field-dependent quasi-particle parameters are deduced from Numerical Renormalization Group calculations for a single Anderson impurity. In filled skutterudites containing the non-Kramers Pr ions, on the other hand, the heavy quasi-particle mass can be explained by aspherical Coulomb scattering of conduction electrons off Crystalline Electric Field excitations. The field-induced splitting of the low-lying triplet should lead to a strongly field-dependent mass enhancement. It is suggested that a field-induced Kondo effect could occur in the dilute system La 1−x Pr x Os 4 Sb 12 in close analogy to the Kondo effect found in integer-spin quantum dots.

Heavy Quasiparticles in Yb Compounds: The Renormalized Band Approach

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