Inertial dynamics of pinned charge-density-wave condensates. II. OrthorhombicTaS3

Abstract

Complex conductivity ${\sigma }_{\mathrm{CDW}(\mathrm{\omega }}$,T) measurements in the ranges 10–110 GHz and 20–300 K are reported on the charge-density-wave (CDW) material orthorhombic ${\mathrm{TaS}}_3$. In the CDW state between approximately 130 and 210 K, the complex conductivity obeys a Drude behavior ${\sigma }_{\mathrm{CDW}}$(ω)=(${\mathrm{ne}}^2$τ/$m^{\mathrm{*}}$)(1+i ωτ), which we associate with damped inertial response of the CDW. The measurements, together with earlier results in the radio-frequency spectral range, enable us to extract all the phenomenological parameters: damping constant τ, effective mass $m^{\mathrm{*}}$, pinning frequency ${\omega }_0$, and maximum CDW conductivity ${\sigma }_{\max }$. The experimental results for these parameters are compared with available microscopic theories. The full dynamic response of the CDW between ${10}^7$ and ${10}^{11}$ Hz is also presented and shows the conductivity resonance well below the single-particle gap, representing both the relaxational and inertial dynamic response of the collective CDW mode. A comparison is made to similar results on the related CDW compound ${\mathrm{NbSe}}_3$.