Unusual non-fermi liquid behavior of [formula omitted] analyzed in a single impurity Anderson model with crystal field effects

Abstract

CeNi 9 Ge 4 exhibits unusual non-Fermi liquid behavior with the largest ever recorded value of the electronic specific heat Δ C / T ≅ 5.5 J K - 2 mol - 1 without showing any evidence of magnetic order. Specific heat measurements show that the logarithmic increase of the Sommerfeld coefficient flattens off below 200 mK. In marked contrast, the local susceptibility Δ χ levels off well above 200 mK and already becomes constant below 1 K. Furthermore, the entropy reaches 2 R ln 2 below 20 K corresponding to a four-level system. An analysis of C and χ was performed in terms of an SU ( N = 4 ) single impurity Anderson model with additional crystal electric field (CEF) splitting. Numerical renormalization group calculations point to a possible consistent description of the different low-temperature scales in Δ c and Δ χ stemming from the interplay of Kondo effect and crystal field splitting.