Critical dynamics and domain motion from permittivity of the electronic ferroelectric (TMTTF)2AsF6

Abstract

The quasi one-dimensional organic conductor (TMTTF)2AsF6 shows the charge ordering transition at TCO=101K to a state of the ferroelectric Mott insulator which is still well conducting. We present and interpret the experimental data on the gigantic dielectric response in the vicinity of TCO, concentrating on the frequency dependence of the inverse 1/ε of the complex permittivity ε=ε′+iε′′. Surprisingly for a ferroelectric, we could closely approach the 2nd order phase transition and to deeply reach the critical dynamics of the polarization. We could analyze the critical slowing-down when approaching TCO from both sides and to extract the anomalous power law for the frequency dependence of the order parameter viscosity. Moreover, below TCO we could extract a sharp absorption feature coming from a motion of domain walls which shows up at a frequency well below the relaxation rate.