Electronic States of Single-Component Molecular Conductors [M(tmdt)2]

Abstract

The electronic states of isostructural single-component molecular conductors [M(tmdt)2] (M= Ni, Au, and Cu) are theoretically studied. By considering fragments of molecular orbitals as basis functions, we construct a multiorbital model common for the three materials. The tight-binding parameters are estimated from results of first-principles band calculations, leading to a systematic view of their electronic structures. We find that the interplay between a pπ-type orbital (L) on each of the two ligands and a pdσ-type orbital (Mσ) centered on the metal site plays a crucial role: their energy difference controls the electronic states near the Fermi energy. For the magnetic materials (M= Au and Cu), we take into account Coulomb interactions on different orbitals, i.e., we consider the multiorbital Hubbard model. Its ground-state properties are calculated within mean-field approximation where various types of magnetic structures with different orbital natures are found. An explanation for the experimental results in [Cu(tmdt)2] is provided: The quasi-degeneracy of the two types of orbitals leads to a dual state where localized M$\sigma$ spins appear, and L sites show a nonmagnetic state owing to dimerization. On the other hand, [Au(tmdt)2] locates in the subtle region in terms of the degree of orbital mixing. We propose possible scenarios for its puzzling antiferromagnetic phase transition, involving the Mσorbital in contrast to previous discussions mostly concentrating on the L sector.

11 pages, 10 figures

References in corpus (8)

• Theoretical Aspects of Charge Ordering in Molecular Conductors
• Single-Component Molecular Metals as Multiband π-d Systems
• Magnetic Properties of Ab initio Model for Iron-Based Superconductors LaFeAsO
• NMR Evidence for Antiferromagnetic Transition in the Single-Component Molecular Conductor, [Au(tmdt)_{2}] at 110 K
• Ab initio derivation of multi-orbital extended Hubbard model for molecular crystals
• Multi-Orbital Molecular Compound (TTM-TTP)I_3: Effective Model and Fragment Decomposition
• NMR Evidence for Antiferromagnetic Transition in the Single-Component Molecular System, [Cu(tmdt)${}_2$]
• Intramolecular charge ordering in the multi molecular orbital system (TTM-TTP)I_3

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• Fragment Model Study of Molecular Multi-Orbital System $X$[Pd(dmit)${}_2$]${}_2$
• Electronic states and molecular dynamics of single-component molecular conductors [M(tmdt)${}_2$] (M=Ni, Pt) studied by ${}^{13}$C and ${}^1$H NMR
• A spin-gapped Mott insulator with the dimeric arrangement of twisted molecules Zn(tmdt)${}_2$
• Single-component molecular material hosting antiferromagnetic and spin-gapped Mott subsystems
• Possible Spin-Density Wave on Fermi Arc of Edge State in Single-Component Molecular Conductors [Pt(dmdt)${}_2$] and [Ni(dmdt)${}_2$]
• Fragment-orbital-dependent spin fluctuations in the single-component molecular conductor [Ni(dmdt)${}_2$]