Observation of a uniaxial ferroelectric smectic A phase
Xi Chen, Vikina Martinez, Pierre Nacke, Eva Körblová, Atsutaka Manabe, Melanie Klasen‐Memmer, Guillaume Freychet, Mikhail Zhernenkov, Matthew A. Glaser, Leo Radzihovsky, Joseph E. Maclennan, David M. Walba, Matthias Bremer, Frank Gießelmann, Noel A. Clark
Abstract
We report the observation of the smectic A F , a liquid crystal phase of the ferroelectric nematic realm. The smectic A F is a phase of small polar, rod-shaped molecules that form two-dimensional fluid layers spaced by approximately the mean molecular length. The phase is uniaxial, with the molecular director, the local average long-axis orientation, normal to the layer planes, and ferroelectric, with a spontaneous electric polarization parallel to the director. Polarization measurements indicate almost complete polar ordering of the ∼10 Debye longitudinal molecular dipoles, and hysteretic polarization reversal with a coercive field ∼2 × 10 5 V / m is observed. The SmA F phase appears upon cooling in two binary mixtures of partially fluorinated mesogens: 2N/DIO, exhibiting a nematic (N)–smectic Z A (SmZ A )–ferroelectric nematic (N F )–SmA F phase sequence, and 7N/DIO, exhibiting an N–SmZ A –SmA F phase sequence. The latter presents an opportunity to study a transition between two smectic phases having orthogonal systems of layers.