Electronic State and Magnetic Susceptibility in Orbitally Degenerate (J=5/2) Periodic Anderson Model

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Magnetic susceptibility in a heavy fermion systemis composed of the Pauli term (χₚ) and the Van-Vleck term (χᵥ). The latter comes from the interband excitation, where f-orbital degeneracy is essential. In this work, we study χₚ and χᵥ in the orbitally degenerate (J=5/2) periodic Anderson model for both the metallic and insulating cases. The effect of the correlation between f-electrons is investigated using the self-consistent second-order perturbation theory. The main results are as follows. (i) Sixfold degenerate model: both χₚ and χᵥ are enhanced by a factor of 1/z (z is the renormalization constant). (ii) Nondegenerate model: only χₚ is enhanced by 1/z. Thus, orbital degeneracy is indispensable for enhancement of χᵥ. Moreover, orbital degeneracy reduces the Wilson ratio and stabilizes a nonmagnetic Fermi liquid state.