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(a) The molecular structure and phase sequence of the LC mixture used (measured in free-standing film). (b) The structure of the three-layer (left) and (right) phases represented as the projection of directors (average molecular direction) onto the numbered layers; the slight angular displacements represent the macroscopic helicoidal structure due to the chirality of the system. The structure is quantified via a distortion angle, . The vector polarizations of layers 1–3 in the structure are depicted by the arrows (see Ref. 1).
[(a) and (b)] Resonant x-ray scans at fields of 1.3 and , respectively, confirming the three-layer structure below . (c) Optical transmission vs electric field. Following the initial, small increase at very low fields due to helical unwinding, there are two distinct thresholds at 1.4 and , labeled (1) and (2), respectively.
[(a)–(c)] Photomicrographs taken below threshold (1), at threshold (1), and at threshold (2) in Fig. 2(c), respectively, revealing the textural changes that occur at these thresholds . The bright region in the right-hand side of (c) is the transition to the ferroelectric phase. The lower field threshold is more subtle as it is associated with a transition in the polarization rather than layer periodicity, as indicated by the change in the transient current profile from the single peak observed below the transition, (d), to the double peak above, (e).
Sketch illustrating the three distinct phases exhibited by the sample. At low fields, the usual three-layer structure is observed, transforming to another three-layer phase with different polarization state medium fields. At higher fields the ferroelectric phase is induced. As the field increases the distortion angle reduces.
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