Modeling electron-electron interactions in reduced-dimensional materials: Bond-charge Coulomb repulsion and dimerization in Peierls-Hubbard models

Journal Article · Sun Jul 01 04:00:00 EDT 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.42.475· OSTI ID:6782241

Campbell, D K; Gammel, J T; Loh, Jr, E Y ^[1]

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1. Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM (USA) Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM (USA)

To the conventional Peierls-Hubbard model, involving both on-site ({ital U}) and nearest-neighbor ({ital V}) Coulomb repulsions, we add off-diagonal'' terms, not expressible purely in terms of site densities, representing bond-bond ({ital W}) and mixed bond-site ({ital X}) electron-electron repulsive interactions involving nearest neighbors. We review earlier analyses of these interactions and discuss relative magnitudes of the parameters in applications to real materials. As a specific illustration, we investigate the effects of the off-diagonal {ital W} and {ital X} terms on dimerization in the one-dimensional, half-filled-band Peierls-Hubbard models, which have been widely applied to conjugated polymers (such as trans-polyacetylene) and to related quasi-one-dimensional charge-density wave (CDW) systems. Using both weak- and strong-coupling perturbation theory for large systems and exact diagonalizations of small systems, we investigate thoroughly the nature of the ground state of the model. For a broad range of the site-diagonal Hubbard parameters ({ital U},{ital V}), including the values believed to be relevant to trans-polyacetylene, we find that the off-diagonal terms ({ital W},{ital X}) initially {ital enhance} dimerization, thereby stabilizing the dimerized (or bond-order-wave (BOW)) ground state. For (unphysically) large values of {ital W} relative to {ital U} and {ital V}, dimerization is destroyed, and the BOW ground state goes over to a ferromagnetic ground state or a CDW ground state, depending on the relative sizes of {ital U}, {ital V}, and {ital W}. We conclude with a general discussion of the applicability of the Peierls-Hubbard models to quasi-one-dimensional materials, including the potential importance of the breaking of charge conjugation ( particle-hole'') symmetry by the {ital X} term.

• OSTI ID: 6782241
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 42:1; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

656002* -- Condensed Matter Physics-- General Techniques in Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CHEMICAL REACTIONS
CRYSTAL MODELS
DIMERIZATION
ELECTRON-ELECTRON COUPLING
ENERGY LEVELS
FERROMAGNETISM
GROUND STATES
MAGNETISM
MATHEMATICAL MODELS
ONE-DIMENSIONAL CALCULATIONS
PERTURBATION THEORY
POLYMERIZATION
POLYMERS