Microscale structural fluctuations at the melting phase transition of strongly confined achiral and chiral nematics.

Abstract

We report on direct microscopic observations of thermally driven fluctuating dynamics in a narrow temperature region between the isotropic and low-temperature phases in achiral, chiral, and strongly chiral (blue phase) liquid crystal materials. We observe the dynamics in samples strongly confined between two glass surfaces which act as disordering surfaces at thicknesses above the critical confinement thickness below which the phase transition is gradual. In achiral and long-pitch chiral materials the fluctuating appears as formation and disappearance of small structureless nematic domains, whereas in strongly chiral materials, which exhibit blue phase I at larger thicknesses, these fluctuations are real-time formation and annihilation of topologically nontrivial nematic half-skyrmions. We study the dynamics of these fluctuations and present a simple model that explains how such dynamics is possible in ultraconfined systems.