Single-Component Molecular Metals as Multiband π-d Systems(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

Electronic states of single-component molecular metals M (tmdt) 2 ( M = Ni, Au) are studied theoretically. We construct an effective three-band Hubbard model for each material by numerical fitting to first-principles band calculations, while referring to molecular orbital calculations for the isolated molecules. The model consists of two kinds of base orbital for each molecule with hybridization between them, i.e., a π-character orbital for each of the two tmdt ligands, and, a p d π-orbital for M = Ni or a p d σ-orbital for M = Au centered on the metal site; this indicates that these materials can be considered as novel multiband π– d systems. We find that both orbitals contribute to realize the metallic character in Ni(tmdt) 2 . The origin of the antiferromagnetic transition observed in Au(tmdt) 2 is also discussed based on this model.