On the electrical conductivity of intermediate valence compounds

Abstract

The electrical resistivity of the hybridized 4f-(5d/6s) system interacting with LA phonons is calculated by applying the memory function method to the periodic Anderson model in Hartree-Fock approximation. We propose a new mechanism to explain in part the anomalous resistivity of mixed valence compounds such as CePd₃. For finite hybridizationV a finite fraction of 4f electrons participates in electrical conduction leading to an essential change of the normald band current. Resistivity and the fraction of 4f electrons increase with increasing value of [V/(E−μ)]² where (E−μ) is the distance between the effective positionE of the 4f level and the chemical potential. In typical mixed valence systems [V/(E−μ)]² is strongly temperature dependent and decreases with increasing temperature. This explains the high temperature resistivity behaviour of CePd₃. For (E−μ) being small compared to the Debye-temperature the resistivity is enhanced and becomes extremely sensitive to small changes of (E−μ).