Non-stripe charge order in dimerized organic conductors

Abstract

This paper demonstrates charge order is important in dimerized $\ensuremath{\beta}$- and $\ensuremath{\kappa}$-phase organic conductors similar to the uniform $\ensuremath{\theta}$- and $\ensuremath{\alpha}$-phase conductors. Here the magnitude of the dimerization represents the deviation from the ideal triangular lattice in analogy with the anisotropy in the $\ensuremath{\theta}$ phase. Since the ratio of the intradimer transfer integral to the interdimer transfer integral is as large as $\ensuremath{\sim}2.6$, these dimerized phases lead to a dimer Mott insulator, whereas the Coulomb repulsion is closer to the triangular lattice because the ratio of the intradimer Coulomb repulsion to the interdimer Coulomb repulsion is comparatively small ($\ensuremath{\sim}1.7$). Accordingly, in the static-limit calculation, non-stripe charge order with threefold periodicity appears between the uniform and the stripe phases, and the analogy with the $\ensuremath{\theta}$ phase suggests the first-order nature of the metal-insulator transition.