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Cholesteric pitch divergence near smectic phase transitions
H G Yoon1, I Dierking, H F Gleeson
1School of Physics and Astronomy, University of Manchester, Oxford Road, United Kingdom.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|September 28, 2010
Summary
This study investigates the pitch divergence in cholesteric liquid crystals near smectic phases. Experimental results support the Chen and Lubensky model for critical exponents, highlighting the importance of fluctuations.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Physical Chemistry
Background:
- Cholesteric liquid crystals exhibit complex phase transitions.
- Understanding critical behavior near smectic-A* (SmA*) and smectic-C* (SmC*) phases is crucial.
- Conflicting theoretical models exist for pitch divergence in these systems.
Purpose of the Study:
- To experimentally investigate the critical behavior of pitch divergence in cholesteric liquid crystals.
- To compare experimental findings with existing theoretical interpretations.
- To determine the critical exponent associated with phase transitions.
Main Methods:
- Studied two homologous series of liquid crystals with N*-SmC* and N*-SmA* polymorphism.
- Employed a modified functionality for temperature dependence of pitch.
- Determined critical exponents, showing independence from sample geometry.
Main Results:
- Experimental critical exponents for pitch divergence align with the Chen and Lubensky model.
- Observed a critical exponent of ν=1/2 for N*-SmA* transitions.
- Observed a critical exponent of ν=1 for N*-SmC* transitions.
Conclusions:
- The study provides evidence supporting the Chen and Lubensky theoretical model.
- Fluctuations play a significant role in the nature of N*-SmA* and N*-SmC* phase transitions.
- Experimental determination of critical exponents offers insight into liquid crystal phase behavior.
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