Charge ordering in θ − ( BEDT − TTF ) 2 Rb Zn ( SCN ) 4 : Cooperative effects of electron correlations and lattice distortions

摘要: Combined effects of electron correlations and lattice distortions on the charge ordering in $\ensuremath{\theta}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{2}\mathrm{Rb}\mathrm{Zn}{(\mathrm{SCN})}_{4}$ are investigated theoretically a two-dimensional $3∕4$-filled extended Hubbard model with electron-lattice couplings. It is known that this material undergoes phase transition from high-symmetry metallic state to low-symmetry insulating horizontal-stripe order (CO) by lowering temperature. By means exact-diagonalization method, we show electron-phonon interactions crucial stabilize CO realize crystal structure.