Spontaneous chiral symmetry breaking in liquid crystals

Motivated by new experimental observations we generalize the Landau-like approach to include the direct phase transition between isotropic liquid (I) and heliconical nematic liquid crystal (N_TB) structure. We show that depending on the Landau expansion coefficients, our model allows either direct I–N_TB transition, or the sequence of the phases I–N–N_TB with the classical nematic liquid crystal (N) sandwiched between the isotropic liquid and heliconical nematic liquid crystal. Which of these two situations is realized depends on how strong is the first order phase transition from the isotropic liquid. If it is strong enough the system undergoes I–N–N_TB sequence, and for the very weak first order phase transition I–N_TB transformation occurs. Furthermore in the latter case the NTB structure can be biaxial heliconical nematic liquid crystal.