Superconductivity in the orbital degenerate model for heavy fermion systems

Takimoto, Tetsuya; Hotta, Takashi; Ueda, Kazuo*

Rich physics is expected to appear due to the coupling between orbital and spin degrees of freedom in strongly correlated electron system with orbital degeneracy. Especially, it is considered that the superconducting transition in orbital degenerate system is one of the most interesting phenomena. For instance, triplet superconductivity occurs in SrRuO where three cylindrical Fermi surfaces are observed. Also, heavy fermion superconductors are considered to have potentially orbital degree of freedom due to large degeneracy of -electron states. We discuss the effect of orbital fluctuations on superconductivity by using random phase approximation and fluctuation exchange (FLEX) approximation. It is also expected that the FLEX approximation is useful to study the correlation between spin and orbital fluctuations for the orbital degenerate system.