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Theory of the thermoelectricity of intermetallic compounds with Ce or Yb ions

The thermoelectric properties of intermetallic compounds with Ce or Yb ions are explained by the single-impurity Anderson model which takes into account the crystal-field splitting of the 4f ground-state multiplet, and assumes a strong Coulomb repulsion which restricts the number of f electrons or f holes to nf ? 1 for Ce and n hole f ? 1 for Yb ions. Imposing the charge neutrality constraint on the local scattering problem at each temperature and pressure, we calculate the excitation spectrum and the transport coefficients of the model by the non-crossing approximation. The thermopower obtained in such a way exhibits all the characteristic features observed in Ce and Yb intermetallics. Assuming that pressure changes the effective coupling, we calculate various characteristic energy scales of the model and obtain the (T, p) phase diagram which agrees with the experimental data on CeRu2Si2, CeCu2Si2, CePd2Si2, and similar compounds. The chemical pressure effects in EuCu2(Ge1 ?x Six)2 are discussed as well. The evolution of the thermopower and the electrical resistance as a function of temperature, pressure or doping is related to the crossovers between various fixed points of the model. The seemingly complicated shape of S(T) is explained in terms of the redistribution of the single-particle spectral weight within the Fermi window.

Strongly Correlated Electron Materials

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