Off-diagonal Coulomb interactions in the extended Peierls-Hubbard model: Exact diagonalization results

Conference · Sun Jan 01 00:00:00 EST 1989

DOI:https://doi.org/10.1007/978-1-4613-0565-1_20· OSTI ID:5821214

Campbell, D K; Gammel, J T; Loh, Jr, E Y

For conjugated polymers, the extended Peierls-Hubbard model has been widely accepted as correctly incorporating the effects of both e-p and e-e interactions. In the absence of e-e interactions, the ground state of (CH)/sub x/ is the 2k/sub F/ bond-order wave (BOW) -- dimerization/bond alternation -- predicted by Peierls theorem. It is now well established that for the weak e-p coupling appropriate to (CH)/sub x/, the on-site Coulomb repulsion actually enhances dimerization up to fairly large values (U > 6t/sub 0/). These results are still widely regarded as counter to the conventional wisdom that Coulomb interactions should suppress the build-up of charge anywhere, on the sites or on the bonds. Since the extended Peierls-Hubbard model incorporates only (lattice) site-diagonal parts of the electron-electron interactions (U, V), and omits the off-diagonal bond-charge repulsions (W,X), it is natural to ask whether this model adequately describes the full consequences of e-e interactions. In the specific context of (CH)/sub x/, the potential importance of this omission is readily recognized. Intuitively, the bond-charge repulsion should suppress dimerization, since it opposes the build-up of charge on the bonds. Thus, the absence of W and X terms in the standard extended Peierls-Hubbard models suggests a priori that these models may artificially favor the continuation of dimerization in the half-filled band into the region of intermediate to strong Coulomb interaction. More generally, the omission of terms such as W and X raises significant questions about the appropriateness of Hubbard models for describing e-e interactions in the whole class of novel solid state materials. Thus this issue is extremely important and is, discussed further in this paper. 14 refs., 6 figs.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5821214
• Report Number(s): LA-UR-89-2520; CONF-8810299-4; ON: DE89015292
• Resource Relation: Journal Volume: 213; Conference: Interacting electrons in reduced dimensions, Torino, Italy, 3-7 Oct 1988; Other Information: Portions of this document are illegible in microfiche products
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ELECTRON-ELECTRON COLLISIONS
COULOMB SCATTERING
ELECTRON-PHONON COUPLING
COULOMB FIELD
DIMERIZATION
DIMERS
HAMILTONIANS
PEIERLS METHOD
PERTURBATION THEORY
PHASE SHIFT
BASIC INTERACTIONS
CHEMICAL REACTIONS
COLLISIONS
ELASTIC SCATTERING
ELECTRIC FIELDS
ELECTROMAGNETIC INTERACTIONS
ELECTRON COLLISIONS
INTERACTIONS
MATHEMATICAL OPERATORS
POLYMERIZATION
QUANTUM OPERATORS
SCATTERING
656002* - Condensed Matter Physics- General Techniques in Condensed Matter- (1987-)