OPTICAL-ACTIVITY OF INCOMMENSURATE STATE OF [N(CH3)4]2CUCL4

By applying the HAUP (high-accuracy universal polarimeter) method, [N(CH3)4]2CuCl4 was found to be optically active in its incommensurate phase, e.g., g23=3. 9×10-5 at 24 °C. The temperature dependence of g 23 was obtained. By making use of the fact that the commensurate phase of [N(CH3)4]2CuCl4 is ferroelastic and centrosymmetric, the temperature dependence of the soliton density in its incommensurate phase was deduced by this optical measurement. It is suggested that the HAUP method will become a new and direct method for measuring soliton densities of incommensurate states.