Low frequency dielectric permittivity of quasi-one-dimensional conductor (TMTTF)2Br

Conductivity and permittivity epsilon of the organic transfer salt (TMTTF)(2)Br have been measured at low frequencies (10(2)-10(7) Hz) between room temperature down to 4 K. The real part of the permittivity, EI, is shown to grow below the temperature T-rho at which the conductivity is maximum due to charge localization of Mott-Hubbard type. epsilon' reaches a maximum of 10(5)-10(6) at 35 K-50 K depending on the samples. Decreasing temperature below T-rho, sharply decreases down to helium temperature through the antiferromagnetic phase transition at TN = 15 K. We explain the magnitude, the temperature and frequency dependence of epsilon' as resulting from short range charge density wave states in the temperature range where charge localization occurs. This interpretation is supported by recent X-ray scattering measurements.