报告题目：Director Deformations, Geometric Frustration, and Modulated Phases in Liquid Crystals
报告时间：2023 年 11月 2 日 (周四) 上午10:00
报告人：Prof. Jonathan Selinger
Biography: Jonathan Selinger is Professor of Physics and Ohio Eminent Scholar at Kent State's Liquid Crystal Institute. His research focuses on the theory of liquid crystals, nanoparticle suspensions, and related topics in soft materials, and seeks to make connections between fundamental statistical mechanics and technological applications.
Selinger studied physics at Harvard University, receiving his A.B. in 1983 and Ph.D. in 1989. He then did postdoctoral research in Los Angeles, with positions at the UCLA Department of Physics and Caltech Department of Chemical Engineering. In 1992 he moved to the Naval Research Laboratory in Washington, DC, where he worked as a Research Physicist in the Center for Bio/Molecular Science and Engineering. In 2005 he came to his current position at Kent State. In addition to these research and teaching positions, he has also served as Associate Editor of Physical Review E, responsible for the liquid-crystal section of the journal, and he is currently Treasurer of the International Liquid Crystal Society.
Abstract: In this talk, we analyze modulated phases in liquid crystals, from the long-established cholesteric and blue phases to the recently discovered twist-bend, splay-bend, and splay nematic phases, as well as the twist-grain-boundary (TGB) and helical nanofilament variations on smectic phases. The analysis uses the concept of four fundamental modes of director deformation: twist, bend, splay, and a fourth mode related to saddle-splay. Each mode is coupled to a specific type of molecular order: chirality, polarization perpendicular and parallel to the director, and octupolar order. When the liquid crystal develops one type of spontaneous order, the ideal local structure becomes nonuniform, with the corresponding director deformation. In general, the ideal local structure is frustrated; it cannot fill space. As a result, the liquid crystal must form a complex global phase, which may have a combination of deformation modes, and may have a periodic array of defects. Thus, the concept of an ideal local structure under geometric frustration provides a unified framework to understand the wide variety of modulated phases.