Metal–Insulator Transition of the New One-Dimensional Organic Conductors with Complete Uniform Stacks: (DMEDO-TTF)₂X(X= ClO₄and BF₄)

Bond patterns and charge-order amplitude in quarter-filled charge-transfer solids

“…In each of these materials the MI transition has been attributed to different effects, such as e-p and coupled molecular bending [7] or electrical potential bias originating from long-range Coulomb interactions [6] in (EDO-TTF) 2 X, and anion ordering in (DMEDO-TTF) 2 X [8]. We argue that these are instead cooperative effects [3] (see below).…”

“…The authors of Ref. [8] ascribe the MI transition to this anion shift, in which the ClO 4 group moves towards and away from charge-rich and charge-poor molecules. The electrostatic potential of the anions enhances n of the organic stack, which further strengthens the strong "S" bond.…”

“…A similar material is * r.t.clay@msstate.edu (DMEDO-TTF) 2 X, X = ClO 4 and BF 4 , where there is also a single transition. It has been proposed that anions drive the transition [8]. The CO amplitude is currently unknown.…”

“…Molecular bending [7] and cation-anion interactions [8] act cooperatively with the underlying bond distortion of the organic stacks. Through a systematic numerical study, we show that with increasing e-e interaction strength, a crossover occurs between two different bond-charge-density waves (BCDWs), which we will label BCDW1 and BCDW2 (see Fig.…”

“…7(c) of Ref. [8]] moves the hole-rich molecules closer to the anions. This feedback loop between the anions and the bond distortion will cooperatively strengthen BCDW2.…”