Q-tensor model of twist-bend and splay nematic phases

Abstract

The twist-bend nematic phase (NTB) is characterized by a conically twisting director and by a dramatic softening of the bend elastic constant before the transition to NTB phase. In the recently found splay nematic phase (NS) the splay elastic constant tends to zero, resulting in a splay modulation perpendicular to the director. We model both phases with a single Q-tensor free energy including a term that breaks the degeneracy between the splay and bend elastic constant, and a flexoelectric term coupling the divergence of the Q-tensor with polarization. NTB or NS phase is obtained by a change of sign of one elastic parameter. Measured elastic constants show that N-NTB transition is mainly driven by the increase of the nematic order, while the NS transition is due to flexoelectric coupling.

7 pages, 3 figures

References in corpus (2)

• Ferroelectric-ferroelastic phase transition in a nematic liquid crystal
• Elastic and viscous properties of nematic dimer CB7CB

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• Twist-bend nematics and heliconical cholesterics: a physico-chemical analysis of phase transitions and related specific properties
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• Double Splay Nematic Order in Confined Polar Fluids
• Mechanochemical Topological Defects in an Active Nematic
• Phase Separation in Mixtures of Nematic and Isotropic Fluids