A NEW MODEL FOR THE MIXED VALENCE COMPOUNDS

The ground-state properties of the Sm-based mixed valence compounds are discussed by means of introducing an indirect on-site hybridization mediated by phonons, for the direct on-site hybridization is forbidden by inversion symmetry. A self-consistent field approximation is used, and a nonzero energy gap and a fluctuating valence state are given. The results obtained can be used to explain the small energy gap and the valence fluctuation phenomena observed in SmB₆ and SmS.