Single-Component Molecular Metals as Multiband \pi-d Systems

TL;DR

This paper develops a multiband Hubbard model for single-component molecular metals M(tmdt)2 (M=Ni, Au) to understand their electronic states, revealing the roles of different orbitals in their metallic and magnetic properties.

Contribution

It introduces a novel three-band Hubbard model for M(tmdt)2, combining molecular orbital calculations with first-principles data, highlighting the multiband b1-d nature of these materials.

Findings

Both orbitals contribute to metallicity in Ni(tmdt)2.

The model explains the antiferromagnetic transition in Au(tmdt)2.

The materials are characterized as multiband b1-d systems.

Abstract

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 \pi-character orbital for each of the two tmdt ligands, and, a pd\pi-orbital for M = Ni or a pd\sigma-orbital for M = Au centered on the metal site; this indicates that these materials can be considered as novel multiband \pi-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.