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Elastic anomaly of heavy fermion systems in a crystalline field

An elastic anomaly, observed in the heavy Fermi liquid state of Ce alloys (for example, CeCu6 and CeTe), is analysed by using the infinite-U Anderson lattice model. Four atomic energy levels are assumed for f-electrons. Two of them are mutually degenerate. A small crystalline splitting 2 Delta is assumed between two energy levels. The fourfold degenerate conduction bands are also considered in the model. The authors solve the model using the mean-field approximation to slave bosons, changing the Fermi energy in order to keep the total electron number constant. The non-zero value of the mean field of the slave bosons persists over temperatures much higher than the Kondo temperature. This is an effect of the constant electron number. Next, the linear susceptibility with respect to Delta is calculated in order to obtain the renormalized elastic constant. The resulting temperature dependence of the constant shows a downward dip. The authors discuss the relation of their findings to experimental data.