Contribution of charge-density-wave phase excitations to thermal conductivity below the Peierls transition

We report on measurements of the thermal conductivity of the quasi-one-dimensional conductor (${\mathrm{NbSe}}_4$ ${)}_{10}$ ${\mathrm{I}}_3$ between 80 and 320 K. We show that the thermal conductivity exhibits a well-defined minimum below the Peierls transition temperature ${\mathit{T}}_{\mathit{p}}$=285 K. Such behavior has also been found in the charge-density-wave (CDW) conductors ${\mathrm{K}}_{0.3}$ ${\mathrm{MoO}}_3$ and (${\mathrm{TaSe}}_4$ ${)}_2$I, and seems to be a generic property of CDW systems. We propose that this feature results from the contribution of low-frequency phasons of rather large velocity. The position of the minimum in the thermal conductivity corresponds to the temperature range where the screening of the Coulomb interaction by the quasiparticles (electron-hole pairs) becomes effective and consequently enables the phason contribution.