Defect-Mediated Phase Transitions

But no other field in condensed matter physics has shown such a rich variety of continuous or weakly first-order phase transitions than liquid crystals order parameters of various symmetries, anisotropic scaling behaviors, coupled order parameters, multicritical points, wide critical domains, defect mediated transitions, spaces of low dimensionality, multiply reentrant topologies are currently found in liquid crystals, at easily accessible temperatures. Beside their famous technical applications in optics... 

The study of stacked hexatics has yielded a complete classification of the large variety of thermotropic liquid crystal phases. It has also presented a single experiment which yields a simultaneous measurement of many crossover anisotropy exponents, previously obtained from separate complex experiments. It is also an excellent system to reveal dimensional crossover and the interplay between two- and three-dimensional physics. For very thin layers, the stacked hexatic layers can be used to extract the hexatic stiffness, or Frank constant, and thus test predictions of defect mediated transition theories. 

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