Microscopic approach to magnetism and superconductivity of -electron systems with filled skutterudite structure

Hotta, Takashi

In order to understand electronic properties of filled skutterudite materials, the Anderson model is analyzed by using the numerical renormalization group method to evaluate magnetic susceptibility and entropy of electron for each case of =113, where is the number of electrons per rare-earth ion. For the -electron system corresponding to the Pr-based filled skutterudite, it is found that magnetic fluctuations significantly remain at low temperatures, even when the ground state is singlet, if triplet is the excited state with small excitation energy. By analyzing an orbital degenerate Hubbard model constructed based on the - coupling scheme, we find that anisotropic Cooper-pair mediated by magnetic fluctuations appears in a limited region in which the singlet and triplet ground states are interchanged.