Normal state electrodynamic properties of charge- and spin-density-wave compounds

We have examined the normal state (T > Tc) optical properties (1–105 cm−1) of low dimensional conductors which exhibit both charge- and spin-density-wave ground states and have found important deviations from simple metallic behavior, especially at low frequencies. In addition to a pseudogap, the optical response parallel to the conducting chains of the charge-density-wave (CDW) compound (TaSe4)2I (Tc = 263 K) shows an enhanced low frequency conductivity which can be described quantitatively as the contribution from fluctuating CDW segments. Similarly, we will present optical measurements performed on the model spin-density-wave (SDW) compound (TMTSF)2PF6 (Tc = 12.1 K). In the metallic state just above Tc, the optical conductivity parallel to the conducting chains has two distinct temperature dependent features: a zero frequency response and a finite energy absorption.