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http://hdl.handle.net/2289/7468| Title: | Saddle-splay-induced periodic edge undulations in smectic-A disks immersed in a nematic medium |
| Authors: | Krishnamurthy, Kanakapura S Rao, Shankar D.S. Kanakala, Madhu B Yelamaggad, C.V. Madhusudana, N.V. |
| Issue Date: | Mar-2020 |
| Publisher: | American Physical Society |
| Citation: | Physical Review E, 2020, Vol.101, Article No.032704 |
| Abstract: | We report experimental studies on the phase behavior of binary mixtures of 1 ,7 -bis(4-cyanobiphenyl-4 -yl)heptane (CB7CB) and 4,4-diheptyloxyazoxybenzene, which exhibit, apart from the nematic (N) and twistbend nematic (NTB) phases, the induced smectic-A (Sm-A) phase for weight fraction of CB7CB between 0.05 and 0.70. In planar nematic layers, the NTB phase separates as droplets of tactoidlike planform; the chirality of droplets manifests in the optical dissimilarity between their opposite angular ends. Our main result is that, in the appropriate two phase region, Sm-A nuclei with positive dielectric anisotropy change over to disks immersed in the nematic above some electric field, their edges decorated by periodic bright spots, a result which was earlier reported in another binary system exhibiting the induced Sm-A phase [R. Pratibha and N. V. Madhusudana, Physica A 224, 9 (1996)]. We develop a simple theory for the threshold of this distortion, which is a periodic undulation of the edge of the disk, demonstrating that it arises from saddle-splay elasticity of Sm-A, the low Sm-A–N interfacial tension unable to suppress the distortion. The observed increases in the number of brightspots with field, and with the radius of the disk at a given field, in both the experimental systems are also accounted for by the model. The distortion, which results in the most direct visualization of saddle splay in Sm-A, is also exhibited by disks nucleating on surfaces treated for homeotropic anchoring. |
| Description: | Open Access |
| URI: | http://hdl.handle.net/2289/7468 |
| ISSN: | 2470-0045 2470-0053 (Online) |
| Alternative Location: | https://doi.org/10.1103/PhysRevE.101.032704. |
| Copyright: | 2020 American Physical Society |
| Appears in Collections: | Research Papers (SCM) |
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| File | Description | Size | Format | |
|---|---|---|---|---|
| 2020_Phys Rev E_Vol.101_Article No.032704.pdf Restricted Access | Open Access | 4.41 MB | Adobe PDF | View/Open Request a copy |
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