Dynamic conductivity of TCNQ salts in the submillimeter wave band

The conductivity and permittivity spectra for four organic one-dimensional conductors based on TCNQ molecules are measured in the submillimeter (8-32/cm) range. The TTF-TCNQ spectra in longitudinal polarization at room temperature are derived according to the dynamics of free electrons excited over the Peierls pseudogap 2Delta = 0.06 eV. A heavily damped mode at about 40/cm is observed in the spectra at low temperatures. Strong relaxation in the MTPA(TCNQ)2 spectra in longitudinal polarization is observed whose contribution varies with the temperature in accordance with the activation law. The results are interpreted on the basis of the interrupted strand model, it being assumed that the submillimeter relaxation response in MTPA(TCNQ)2 is determined by the free electrons inside the quasi-isolated TCNQ tetramers.