Theory of Superconductivity in PuCoGa₅

Abstract

Recently, superconductivity in PuCoGa₅ was discovered. It has the same crystal structure as CeMIn₅ (M=Ir, Co, Rh), which are often refered to as Ce-115’s. The electron correlation in PuCoGa₅ is estimated to be weak compared with Ce-115’s, and the filling number of electrons is considered to be far from 0.5/spin in the band which plays an important role in realizing the superconductivity. Nevertheless, the superconducting transition temperature T_c in PuCoGa₅ is almost by an order of magnitude higher than that in Ce-115’s. In order to explain the superconductivity with high T_c, we adopt the periodic Anderson model and calculate T_c by solving the Dyson–Gor’kov equation derived by the third order perturbation theory with respect to U. By this calculation, we indicate that the superconducting state of PuCoGa₅ is a d-wave pairing state, and show that the good location of two Fermi surfaces results in the high T_c in PuCoGa₅.