Real-time observation of twin boundary motion in organic crystal (TMTSF)2X

Abstract

Ferroelastic domain boundary can be regarded as a type of twin domain boundary. A twin deformation is induced in a conducting organic crystal (TMTSF)2X when the shear stress is applied. TMTSF denotes tetramethyle-tetraselenafulvalene and × does an anion such as CIO4 + and PF6 +. The boundary can move easily along one direction under the small shear stress of about 1 kPa. We could successfully observe the motion of the isolated twin boundary in real time and investigate control parameters of its motion. The motion of the twin boundary is intermittent even under a constant stress. The boundary can move under stress above a small threshold. Temperature dependence of the local velocity strongly depends on the applied stress: when the temperature is lowered, the velocity increases under the small stress while decreases under the large stress. The local velocity depends not only on external stress and temperature but also on the waiting time before the onset of motion.