Effect of quenching rate on SDW dynamics in (TMTSF)2ClO4

The pinning mechanism of SDW condensate associated with the imperfect nesting effect was investigated with the measurement of the temperature dependence of the threshold electric field ET for the depinning of SDW in (TMTSF)2ClO4 for various anion quenching rates. The relatively strong temperature dependence of ET observed in the most rapidly quenched phase with TC=5.85 K is described by the 3-dimensional impurity weak pinning. With decreasing the quenching rate, the temperature dependence of ET becomes gradual for TC > 3 K. This behavior is explained by the change of pinning mechanism to the strong pinning. For much lower quenching rate (TC < 3 K), the temperature dependence of ET becomes steeper again and is attributed to the increase of imperfectness of nesting of Fermi surface. It is understood that the SDW pinning is provided by the disordered array of anion