Raman Spectroscopy of the Charge-Density-Wave State in TaS3

Raman spectroscopy has been used to study the quasi-one-dimensional charge-density-wave (CDW) compound, Ta${\mathrm{S}}_3$. We determine for the first time both the temperature dependence of the CDW order parameter and the magnitude of the electronic gap $2\Delta \mathrm{}\left(T\right)\mathrm{}$ opened by the CDW at the Fermi surface. The transition to the CDW state appears to be continuous; our value of $2\Delta \mathrm{}\left(0\right)\mathrm{}\simeq 530$ ${\mathrm{cm}}^{-1\mathrm{}}$ is in agreement with both theory and transport measurements.