Superconductivity in f-electron systems controlled by crystalline electric fields

Kubo, Katsunori ; Hotta, Takashi

To elucidate the mechanism and controlling parameter of the superconductivity in CeTIn (T=Co, Rh, and Ir), we study an -electron model based on a - coupling scheme on a square lattice. In this study, we consider electrons with total angular momentum =5/2. These states split into one and two doublets under a tetragonal CEF. By choosing appropriate CEF potential, we can control the CEF wave-functions without changing the level splitting. Although the Fermi surface does not change so much as long as the splitting is fixed, the ground state changes depending on the CEF wave-function among paramagnetic, antiferromagnetic, and -wave superconducting states. Thus, in addition to the Fermi-surface topology and the carrier density, the wave-function of the CEF state is an important ingredient to control the appearance of superconductivity in such systems. We will discuss possible relevance of our scenarioto the superconductivity in CeTIn.