Interaction of spin-density waves with defects and quasiparticles

Abstract
The results of recent transport measurements in the spin-density wave (SDW) state of the Bechgaard salts (TMTSF)₂X [X = PF₆, AsF₆, SbF₆, or (AsF₆)_(1-x)(SbF₆)_x] are summarized. The weak nonmagnetic disorder introduced by the alloying of two kinds of anions increases the depinning threshold by up to 3 orders of magnitude. The damping of the low-frequency phase mode decreases exponentially with increasing temperature and saturates at a constant value determined by the disorder at high temperatures. The dc nonlinear conductivity disappears at low temperatures, and this behavior is not explained by the increasing damping. From Hall effect measurements we find a strong coupling between the SDW and normal electrons.