Two-band model for halogen-bridged mixed-valence transition-metal complexes. II : electron-electron correlations and quantum phonons

We study the effects of electron-electron interactions in halogen-bridged mixed-valence transition-metal linear-chain complexes ({ital MX} chains) applying a simple 3/4-filled two-band discrete tight-binding (extended) Peierls-Hubbard model with both on-site and intersite electron-phonon couplings....

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Bibliographic Details
Published in:Physical review. B, Condensed matter Condensed matter, 1992-03, Vol.45 (12), p.6435-6458
Main Authors: WEBER-MILBRODT, S. M, TINKA GAMMEL, J, BISHOP, A. R, LOH, E. Y
Format: Article
Language:English
Subjects:
400202 > Isotope Effects, Isotope Exchange, & Isotope Separation
COMPLEXES
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Electron states
ELECTRON-ELECTRON INTERACTIONS
ENERGY LEVELS
Exact sciences and technology
EXCITED STATES
GROUND STATES
HARTREE-FOCK METHOD
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
INTERACTIONS
ISOTOPE EFFECTS
LEPTON-LEPTON INTERACTIONS
Narrow-band systems
intermediate-valence solids
PARTICLE INTERACTIONS
PERTURBATION THEORY
PHONONS
Physics
QUASI PARTICLES 665000 > Physics of Condensed Matter-- (1992-)
TRANSITION ELEMENT COMPLEXES
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Summary:We study the effects of electron-electron interactions in halogen-bridged mixed-valence transition-metal linear-chain complexes ({ital MX} chains) applying a simple 3/4-filled two-band discrete tight-binding (extended) Peierls-Hubbard model with both on-site and intersite electron-phonon couplings. We employ a variety of methods: perturbation theory, Hartree-Fock approximation, and exact diagonalization in the limit of classical adiabatic phonons, and a variational approach allowing for a finite phonon frequency, i.e., quantum phonons and isotope effect. This variety of methods has proved necessary to obtain a complete picture, due to the structural richness of this model. We investigate the competition between the electron-electron and electron-phonon interactions in a wide range of parameter regimes for both ground and excited states. We focus on values relevant to the {ital MX} chains, probing the experimental variation as {ital X} and {ital M} are varied among {ital X}=Cl, Br, and I and {ital M}=Pt, Pd, and Ni (spanning electron-phonon-interaction-dominated to electron-electron-interaction-dominated materials).
ISSN:0163-1829
1095-3795
DOI:10.1103/PhysRevB.45.6435