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arXiv · 1910.01424

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

Martin Čopič·Alenka Mertelj
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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.

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Martin Čopič, Alenka Mertelj. 2019-10-03. Q-tensor model of twist-bend and splay nematic phases. https://doi.org/10.1103/physreve.101.022704

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