Heavy-fermion state in the Anderson lattice

To investigate theoretically the heavy-fermion state in cerium and uranium compounds, the low-energy excited states in an Anderson lattice are studied at absolute zero. The coupled Dyson equations for both the Greens functions of the f electron and the spin fluctuations are set up in the case of the finite correlation interaction energy. The vertex functions are approximately determined to fulfill the Ward-Takahashi relations which originate from the spin-rotational invariance, in the low-energy region. In the spectral density of the f-electron Greens function which is numerically calculated, it is found that a sharp peak corresponding to the state of quasifermions with heavy masses appears near the Fermi level, and a broad peak similar to the resonance peak in Kondo impurity systems appears in a relatively-high-energy region. As the temperature increases, the quasifermion peak diminishes and changes to the resonance peak.