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First-order Landau-de Gennes model for layer thinning in presmectic free-standing films.
1Department of Physics and Guelph-Waterloo Physics Institute, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
Summary
This study presents a Landau theory for ordering in free-standing smectic-A films. It reveals three distinct phases and a power-law relationship for surface-enhanced ordering, crucial for understanding thin film behavior.
Area of Science:
- Physics
- Materials Science
- Soft Matter Physics
Background:
- Smectic-A films exhibit complex phase behaviors, especially in confined geometries.
- Understanding surface effects is critical for predicting thin film properties.
- De Gennes's presmectic model provides a foundation for studying liquid crystal phases.
Purpose of the Study:
- To develop a Landau theory for surface-enhanced ordering in free-standing smectic-A films.
- To investigate phase transitions in systems with a first-order smectic-isotropic transition.
- To characterize the temperature-thickness boundary between different ordered phases.
Main Methods:
- Generalization of de Gennes's presmectic model.
- Application of Landau theory to surface phenomena in thin films.
- Analysis of phase transitions in free-standing smectic-A films.
Main Results:
- The system exhibits three distinct phases: isotropic liquid, bulk-like smectic-A, and a surface-ordered quasismectic phase.
- A temperature-thickness boundary separates the bulk-ordered and surface-ordered phases.
- This boundary follows a power-law relation, similar to layer-thinning transitions.
Conclusions:
- The developed Landau theory effectively describes surface-enhanced ordering in smectic-A films.
- The identified quasismectic phase and power-law behavior are key findings for thin film physics.
- This work contributes to the understanding of phase transitions in reduced dimensions.