Theory of Orbital Fluctuation and Electrical Transport in Unconventional Charge Density Wave Phase of Skutterudite PrRu4P12

Abstract

A theory of charge density wave (CDW) ordering and the metal–insulator transition in skutterudite PrRu 4 P 12 is presented. We introduce a simplified model Hamiltonian which involves an interaction of conduction electrons with localized f electrons occupying singlet–triplet crystal field levels, and calculate the solutions of the coherent potential approximation. It is shown that the fluctuation of the f -electron occupancy plays very important roles in the mechanism of unusual transport properties. On the one hand, the fluctuation leads to a severe suppression of the quasi-particle gap in the CDW phase and resultingly produces a characteristic temperature dependence of the resistivity. On the other hand, the fluctuation induces breaking of the particle–hole symmetry, giving a drastic enhancement of the Hall conductivity in the CDW phase. The mechanism of sign reversal of the Hall conductivity is discussed in connection with the properties of the fluctuation. Comparisons of the theoretical results with th...