Charge-density-wave-phase—mode evidence in one-dimensionalK0.3MoO3

Reflectivity measurements in the far-infrared region irrefutably show the consequence of the Peierls instability in the blue bronze ${\mathrm{K}}_{0.3}$ ${\mathrm{MoO}}_3$ system. At 5 K, a very strong polarization-dependent phonon spectrum is observed: At photon energies below 8 meV, a giant, nearly undamped structure dominates the whole spectrum polarized along the $b$ axis. The structure, reaching reflectivity values of 97%, is assigned to the oscillation of the pinned Fröhlich charge-density-wave (CDW) ($A_{-}$) mode. Optical constants are calculated by means of the Kramers-Kronig relation. The results are compared to the predictions of mean-field theory ($m_{\mathrm{CDW}}^{*}$,$\lambda$,$T_c^{\mathrm{MF}}$) and to the experimental results on ${\mathrm{K}}_2$ ${\mathrm{Pt}\left(\mathrm{CN}\right)\mathrm{}}_4$ ${\mathrm{Br}}_{0.3}$ ${\mathrm{·}3\mathrm{H}}_2$O (KCP). No softening of the ($A_{-}$) mode or of the CDW energy-loss spectrum was observed. A midgap absorption can be related to the presence of solitons (dislocations in CDW lattice) and will be discussed with the latest results on the non-Ohmic conductivity.