CHARGE-DENSITY-WAVE PARACONDUCTIVITY

The dynamic conductivity and permittivity spectra of K0.3MoO3 and (TaS e4)(2)I Single crystals in the conducting phase (above 180 K and 260 K , respectively) have been measured, for the first time, over a broad f requency range 1-10(5) cm(-1), using a combination of different spectr oscopic techniques. In both compounds clearly pronounced excitations a re discovered in the spectra below 50 cm(-1) for the electric field pa rallel the chains, the direction along which the charge density wave d evelops at low T. We associate these excitations with charge-density-w ave fluctuations which exist even at room temperature and give a colle ctive contribution to the conductivity. For the transverse polarizatio n, (E) over right arrow perpendicular to the chains, a usual single-pa rticle Drude behavior of the conductivity and permittivity spectra is observed. The experiments give clear evidence for important deviations from conventional metallic behavior in the fluctuating region, below T-MF but above T-CDW, the temperature where long range order develops.