Relaxation Phenomena in Motion of Isolated Twin Boundary in (TMTSF)2PF6

The twin boundary (kink) induced in (TMTSF)2X moves easily under external force. Its motion is intermittent even under constant stress. Both the velocity and the intermission time depend strongly on stress. We found that the motion is determined not only by stress, but also by tH, the time elapsed before the kink passes forward through a position after the preceding backward passage. When the kink moves after longer tH, the velocity is low and the intermission time is long. Both become constant at tH ~ 103 seconds. We found that the crystal but not the kink itself changes during the backward motion, and the change relaxes during tH. We report on the relaxation process and its effect to kink motion. Effects of applied stress are also presented.