Charge Order in (TMTTF)2TaF6 by Infrared Spectroscopy

We have performed infrared spectroscopy in (TMTTF)2TaF6 (TMTTF: tetramethyltetrathiafulvalene) to investigate the relationship between the charge order (CO) state and the antiferromagnetic (AF) insulating ground state. A clear peak splitting corresponding to the charge disproportionation was observed below the CO transition temperature. We estimated the degree of charge disproportionation, Δρ = ρrich − ρpoor, as 0.28e from the peak splitting and found that the CO state coexists with the AF state and there is no charge redistribution below the AF transition.