Goldstone mode and molecular relaxation in the smectic I* and smectic C* phases

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Abstract
Dielectric studies of the ferroelectric liquid crystalline smectic C* and I* phases of the ZLI-4004 mixture have been carried out. For both phases complex electric permittivity has been measured versus temperature in the frequency range between 0.66 kHz and 10 MHz. In the smectic I* phase two relaxation mechanism have been found, viz. the Goldstone mode coming from phase fluctuations of the director and the low frequency molecular relaxation connected with the reorientation of molecule around the short axis. Two-dimensionally ordered and tilted smectic I* phase exhibits the low frequency molecular relaxation in both directions: parallel and perpendicular to the layer planes. This effect has been found experimentally for the first time for the highly ordered biaxial smectic I* phase. In the smectic C* phase there is a pronounced conductivity component which disturbs both the Goldstone mode and molecular relaxation. Due to this effect there is also a small evidence of the soft mode at the smectic C*—smectic A transition.