Effects of Electron-Lattice Coupling on Charge Order in θ-(ET)2X

Abstract

Charge ordering accompanied by lattice distortion in quasi-two dimensional organic conductors θ-(ET)2X (ET=BEDT-TTF) is studied by using an extended Hubbard model with Peierls-type electron-lattice couplings within the Hartree-Fock approximation. It is found that the horizontal-stripe charge-ordered state, which is experimentally observed in θ-(ET)2RbZn(SCN)4, is stabilized by the self-consistently determined lattice distortion. Furthermore, in the presence of the anisotropy in nearest-neighbor Coulomb interactions Vij, the horizontal charge order becomes more stable than any other charge patterns such as diagonal, vertical and 3-fold-type states. At finite temperatures, we compare the free energies of various charge-ordered states and find a first-order transition from a metallic state with 3-fold charge order to the insulating state with the horizontal charge order. The role of lattice degrees of freedom in the realization of the horizontal charge order and the relevance to experiments on θ-(ET)2X are discussed.

References in corpus (3)

• Quantum Melting of Charge Order due to Frustration in Two-Dimensional Quarter-Filled Systems
• Novel Charge Order and Superconductivity in Two-Dimensional Frustrated Lattice at Quarter Filling
• The Origin of the Charge Ordering and Its Relevance to Superconductivity in $\theta$-(BEDT-TTF)${}_2$X: The Effect of the Fermi Surface Nesting and the Distant Electron-Electron Interactions

Cited by in corpus (3)

• Coexistence of distinct charge fluctuations in $\theta$-(BEDT-TTF)${}_2$X
• Charge ordering in θ-(BEDT-TTF)2RbZn(SCN)4: Cooperative effects of electron correlations and lattice distortions
• Spin and Charge Fluctuations and Lattice Effects on Charge Orders in α-(BEDT-TTF)_2I_3