Charge-density-wave paraconductivity inK0.3MoO3

The dynamic conductivity has been measured in ${\mathrm{K}}_{0.3}$ ${\mathrm{MnO}}_3$ single crystals in the conducting phase (above 180 K), for the first time over a broad frequency range 1-${10}^5$ ${\mathrm{cm}}^{\mathrm{-}1}$, using a combination of different spectroscopic techniques. Together with a pseudogap, clearly pronounced excitations are observed below 50 ${\mathrm{cm}}^{\mathrm{-}1}$ for E→∥b, the direction along which the charge density wave develops. We associate these excitations with charge-density-wave fluctuations which exist even at room temperature and give a collective contribution to the conductivity. For the transverse polarization, E→⊥b, a usual single-particle Drude behavior of the conductivity is observed.