Single-component molecular metals as multiband - systems

Seo, Hitoshi; Ishibashi, Shoji*; Okano, Yoshinori*; Kobayashi, Hayao*; Kobayashi, Akiko*; Fukuyama, Hidetoshi*; Terakura, Kiyoyuki*

Electronic states of single-component molecular metals M(tmdt) (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 -character orbital for each of the two tmdt ligands, and, a pd-orbital for M=Ni or a pd-orbital for M=Au centered on the metal site; this indicates that these materials can be considered as novel multiband -d systems. We find that both orbitals contribute to realize the metallic character in Ni(tmdt). The origin of the antiferromagnetic transition observed in Au(tmdt) is also discussed based on this model.