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The phason dispersion in the antiferroelectric Sm-CA* liquid crystalline phase of 4-(1-methylheptyloxycarbonyl)phenyl 4'-octyloxybiphenyl-4-carboxylate has been studied by quasielastic light-scattering experiments. The phason is found to be gapless as predicted for a Goldstone mode recovering the broken continuous symmetry. The dispersion has a minimum at q=2qc, where qc is the wave vector of the unperturbed Sm-CA* structure. These results are consistent with the alternating-tilt model of the antiferroelectric Sm-CA* phase.
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Muševič et al. (1993) studied this question.
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