We study the Monte Carlo dynamics of strongly correlated classical particles coupled to lattice degrees of freedom in one-dimension relevant to the organic materials tetrathiafulvalene-chloranil (TTF-CA) and tetrathiafulvalene-bromanil (TTF-BA). These particles, carrying spin and subject to strong Coulomb repulsion, undergo a neutral-to-ionic transition as alternating site potentials decrease, leading to charge transfer to higher-energy sites. There is an enhancement of conductivity near the transition, carried by diffusive motion of thermally activated neutral-ionic domain walls (NIDWs). By including local lattice dimerization, we find that NIDW motion becomes subdiffusive and conductivity increases by an order of magnitude. These results underscore the crucial role of local and fluctuating dimerization in controlling transport and ferroelectric behavior near the neutral-ionic transition.

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• Defects
• Diffusion
• Domains
• Electrical conductivity
• Ferroelectricity
• Lattice dynamics
• 1-dimensional systems
• Lattice models in condensed matter
• Monte Carlo methods