Dynamical response of the spin-density-wave mode in tetramethyltetraselenofulvalene hexafluorophosphate [(TMTSF)2PF6]

We report frequency-dependent conductivity measurements in the organic conductor tetramethyltetraselenofulvalene hexafluorophosphate [(TMTSF)2PF6]. The conductivity increases with increasing frequency in the spin-density-wave (SDW) state, providing direct evidence for a collective response due to SDW's. A comparison is made with similar observations in charge-density-wave systems. © 1982 The American Physical Society.