Periodic splay Fréedericksz transitions in a ferroelectric nematic.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39920135.
- Also identified by DOI 10.1038/s41467-025-55827-9 and PMC identifier 11806116.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Electric field-induced splay of molecular orientation, called the Fréedericksz transition, is a fundamental electro-optic phenomenon in nonpolar nematic liquid crystals. In a ferroelectric nematic N<sub>F</sub> with a spontaneous electric polarization <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>P</mi></math> , the splay is suppressed since it produces bound electric charges. Here, we demonstrate that an alternating current (ac) electric field causes three patterns of N<sub>F</sub> polarization. At low voltages, <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>P</mi></math> oscillates around the field-free orientation with no stationary deformations. As the voltage increases, the polarization acquires stationary distortions, first splay and twist in a stripe pattern and then splay and bend in a square lattice of +1 and -1 defects. In all patterns, <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>P</mi></math> oscillates around the stationary orientations. The stationary bound charge is reduced by a geometrical "splay cancellation" mechanism that does not require free ions: the charge created by splay in one plane is reduced by splay of an opposite sign in the orthogonal plane.