We theoretically investigate charge ordered states on the anisotropic triangular lattice characteristic of the θ-(BEDT-TTF)2X materials. Using exact diagonalization studies, we establish that the charge order (CO) pattern corresponds to a "horizontal" stripe structure, with ... 1100... CO along the two directions with larger electron hopping (p-directions), and ... 1010... CO along the third direction (c-direction). The CO is accompanied by co-operative bond dimerizations along all three directions in the highest spin state. In the lowest spin state bonds along the p-directions are tetramerized. Our theory explains the occurrence of a charge-induced high temperature transition as well as a spin gap transition at lower temperature.
- Charge ordering
- Charge-density wave
- Spin gap
ASJC Scopus subject areas
- General Physics and Astronomy