Persistent quasiplanar nematic texture: Its properties and topological defects.

Area of Science:

• Liquid Crystal Physics
• Soft Matter Science
• Materials Science

Background:

• Nematic liquid crystals exhibit unique director field behaviors under confinement.
• The quasiplanar texture, characterized by a director field rotating by π, is known to be metastable.
• The orientation of the director field at mid-layer is sensitive to perturbations.

Purpose of the Study:

• To investigate the stability and behavior of the quasiplanar texture in nematic liquid crystals.
• To introduce and define the "dowser texture" and "dowser field" for a long-lived quasiplanar state.
• To explore the influence of sample thickness gradients on the director field orientation.

Main Methods:

• Experimental observation of liquid crystal textures in confined geometries.
• Theoretical modeling using principles of continuum mechanics and elasticity.
• Analysis of director field behavior under varying thickness conditions.

Main Results:

• The quasiplanar texture, termed the dowser texture, can be infinitely preserved, challenging previous notions of metastability.
• The director field (dowser field) in variable thickness samples aligns with the thickness gradient, a phenomenon termed cuneitropism.
• The dowser field dynamics are described by the sine-Gordon equation, showing solitonic behavior.

Conclusions:

• The dowser texture represents a stable, long-lived state of quasiplanar nematic liquid crystals.
• Cuneitropism demonstrates a novel coupling between director field orientation and sample geometry.
• The sine-Gordon model accurately predicts the behavior of the dowser field, highlighting its solitonic nature.