### Abstract

We examine two recently proposed models of charge ordering (CO) in the nominally 1/4-filled, quasi-onedimensional (1D) organic charge-transfer solids (CTS). The two models are characterized by site charge density "cartoons" ... 1010 ... and ... 1100 ..., respectively. We use the Peierls-extended Hubbard model to incorporate both electron-electron (e-e) and electron-phonon (e-ph) interactions. We first compare the results, for the purely electronic Hamiltonian, of exact many-body calculations with those of Hartree-Fock (HF) mean-field theory. We find that HF gives qualitatively and quantitatively incorrect values for the critical nearest-neighbor Coulomb repulsion (V_{c}) necessary for ... 1010 ... order to become the ground state. Second, we establish that spin-Peierls order can occur in either the ... 1100 ... and ... 1010 ... states and calculate the phase diagram including both on-site and intrasite e-ph interactions. Third, we discuss the expected temperature dependence of the CO and metal-insulator transitions for both ... 1010 ... and ... 1100 ... CO states. Finally, we show that experimental observations clearly indicate the ... 1100 ... CO in the 1:2 anionic CTS and the (TMTSF)_{2}X materials, while the results for (TMTTF)_{2}X with narrower one-electron bandwidths are more ambiguous, likely because the nearest-neighbor Coulomb interaction in these materials is near V_{c}.

Original language | English (US) |
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Article number | 115121 |

Pages (from-to) | 1151211-1151219 |

Number of pages | 9 |

Journal | Physical Review B - Condensed Matter and Materials Physics |

Volume | 67 |

Issue number | 11 |

State | Published - Mar 1 2003 |

### ASJC Scopus subject areas

- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics

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## Cite this

*Physical Review B - Condensed Matter and Materials Physics*,

*67*(11), 1151211-1151219. [115121].