Anomalous Electric Field Dependence of Helical Pitches in Ferroelectric Sm C* at Temperatures Close to the Phase Transition to Sm A

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Abstract
The field dependence of the helical pitches in 2-methylbutyl p-(p-n-hexyloxybenzylideneamino) cinnamate has been studied optically using a homogeneously aligned cell of high quality. Near the phase transition from Sm C* to Sm A, the helical pitch depends on the applied field to a much greater extent than that predicted by the unwinding mechanism of the helicoidal structure based on the assumption that the tilt angle is independent of the field. This fact suggests that thermal fluctuations in the tilt angle play an important role in the unwinding mechanism.