Infrared signature of the charge-density-wave gap in ZrTe<Subscript>3</Subscript>

The chain-like ZrTe<Subscript>3</Subscript> compound undergoes a charge-density-wave (CDW) transition at T<Subscript>CDW</Subscript>=63 K, most strongly affecting the conductivity perpendicular to the chains. We measure the temperature (T) dependence of the optical reflectivity from the far infrared up to the ultraviolet with polarized light. The CDW gap Δ(T) along the direction perpendicular to the chains is compatible for T>T<Subscript>CDW</Subscript> with the behavior of an order parameter within the mean-field Bardeen-Cooper-Schrieffer (BCS) theory. Δ(T) also persists well above T<Subscript>CDW</Subscript>, which emphasizes the role played by fluctuation effects. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2005