Phase competitions and coexistences in quasi-one-dimensional molecular conductors; Exact diagonalization study

Otsuka, Yuichi*; Seo, Hitoshi; Motome, Yukitoshi*; Kato, Takeo*

We investigate ground state properties of a quasi-one-dimensional electron-lattice coupled model for quarter-filled molecular conductors. The effective one-dimensional extended Hubbard model coupled to adiabatic lattice degree of freedom is derived by the inter-chain mean-field approximation and solved by Lanczos exact diagonalization method. We find that the critical behavior among lattice tetramerized states with different charge-lattice ordered patterns is sensitively affected by the inter-chain Coulomb interaction, lattice anharmonicity, and intrinsic dimerization.