X-ray scattering and electric field studies of the sliding mode conductor NbSe3

X-ray scattering studies of Nb${\mathrm{Se}}_3$ show the formation of two independent, incommensurate charge-density waves (CDW) with wave vectors ${\overrightarrow{\mathrm{q}}}_1=(0, 0.243, 0)$ and ${\overrightarrow{\mathrm{q}}}_2=(0.5, 0.263, 0.5)$ at $T_1=144\mathrm{}$ K and $T_2=59\mathrm{}$ K, respectively. Electric fields that suppress the resistive anomaly associated with the lower-temperature CDW have no measurable effect on either the CDW amplitude or wave vector. The field required for suppression appears to scale roughly with the defect concentration as measured by the residual-resistance ratio. These results are consistent with the Fröhlich sliding-CDW model with impurity pinning.