Manifold of polar smectic liquid crystals with spatial modulation of the order parameter.

We revisit a theoretical approach based on the discrete Landau model of polar smectic liquid crystals. Treating equilibrium structures on many length scales, we have analyzed different periodically modulated polar smectic phases. Besides already known smectic structures, we have obtained a number of other phases which are stable in a narrow range (that is why the phases can be termed as microphases) of model parameters and thermodynamic conditions. The sequence of microphases represents a so-called "harmless staircase" of structures with oscillating periods. We anticipate that the range of stabilities for various microphases can be extended (and therefore the microphases can be easier to detect experimentally) by applying external electric fields or/and investigating freestanding smectic films.