COMMENSURATE SPIN-DENSITY-WAVE STATE IN (TMTTF)2BR - SINGLE-PARTICLE AND COLLECTIVE CHARGE DYNAMICS

We report the first transport characterization of a unique commensurat e spin-density wave state of the organic charge insulator (TMTTF)2 Br. An additional anomaly in d.c. resistivity is observed at 22 K, above the SDW transition temperature T(c) = 12.5 K. Non-Ohmic current-voltag e characteristics with sharp threshold fields of the order of 1-10 V/c m are observed in the SDW state. The threshold field is thermally acti vated at low temperatures and increases again close to T(c). Propertie s of the low-frequency dielectric response and the sliding state indic ate a novel charge dynamics associated with this SDW condensate.