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.

arXiv comment7 pages, 3 figures

References in corpus (7)

• Nematic twist-bend phase with nanoscale modulation of molecular orientation
• A Twist-Bend Chiral Helix of 8nm Pitch in a Nematic Liquid Crystal of Achiral Molecular Dimers
• Ferroelectric-ferroelastic phase transition in a nematic liquid crystal
• Statistical mechanics of bend flexoelectricity and the twist-bend phase in bent-core liquid crystals
• Elastic and viscous properties of nematic dimer CB7CB
• Splay nematic phase
• Modulated nematic structures induced by chirality and steric polarization

Cited by in corpus (14)

• First-Principles Experimental Demonstration of Ferroelectricity in a Thermotropic Nematic Liquid Crystal: Spontaneous Polar Domains and Striking Electro-Optics
• Ferroelectric-ferroelastic phase transition in a nematic liquid crystal
• Development of polar nematic fluids with giant-\k{appa} dielectric properties
• Ferroelectric nematic liquid crystalline phases
• Electrooptics of mm-scale polar domains in the ferroelectric splay nematic phase
• Antiferroelectric Smectic Ordering as a Prelude to the Ferroelectric Nematic:Introducing the Smectic $Z_A$ Phase
• Theory of the splay nematic phase: Single vs. double splay
• Twist-bend nematic phase from Landau-de Gennes perspective
• Flexoelectricity versus Electrostatics in Polar Nematic Liquid Crystals
• Twist-bend nematics and heliconical cholesterics: a physico-chemical analysis of phase transitions and related specific properties
• Modulated phases of nematic liquid crystals induced by tetrahedral order
• Double Splay Nematic Order in Confined Polar Fluids
• Mechanochemical Topological Defects in an Active Nematic
• Phase Separation in Mixtures of Nematic and Isotropic Fluids