DOI: 10.1073/pnas.1721786115
论文题名: Nematic twist-bend phase in an external field
作者: Pająk G. ; Longa L. ; Chrzanowska A.
刊名: Proceedings of the National Academy of Sciences of the United States of America
ISSN: 0027-8424
出版年: 2018
卷: 115, 期: 44 起始页码: E10303
结束页码: E10312
语种: 英语
英文关键词: Chirality
; Nematics
; Polarity
; Splay-bend
; Twist-bend
Scopus关键词: anisotropy
; article
; chirality
; entropy
; phase transition
; polarization
英文摘要: The response of the nematic twist-bend (NTB) phase to an applied field can provide important insight into the structure of this liquid and may bring us closer to understanding mechanisms generating mirror symmetry breaking in a fluid of achiral molecules. Here we investigate theoretically how an external uniform field can affect structural properties and the stability of NTB. Assuming that the driving force responsible for the formation of this phase is packing entropy, we show, within Landau-de Gennes theory, that NTB can undergo a rich sequence of structural changes with the field. For the systems with positive anisotropy of permittivity, we first observe a decrease of the tilt angle of NTB until it transforms through a field-induced phase transition to the ordinary prolate uniaxial nematic phase (N). Then, at very high fields, this nematic phase develops polarization perpendicular to the field (Np+). For systems with negative anisotropy of permittivity, the results reveal new modulated structures. Even an infinitesimally small field transforms NTB to its elliptical counterpart (NTBe), where the circular base of the cone of the main director becomes elliptic. With stronger fields, the ellipse degenerates to a line, giving rise to a nonchiral periodic structure, the nematic splay- bend (NSB), where the two nematic directors are restricted to a plane. The three structures-NTB, NTBe, and NSB-with a modulated polar order are globally nonpolar. But further increase of the field induces phase transitions into globally polar structures with nonvanishing polarization along the field's direction. We found two such structures, one of which is a polar and chiral modification of NSB, where splay and bend deformations are accompanied by weak twist deformations (N∗ SBp). Further increase of the field unwinds this structure into a polar nematic (Np) of polarization parallel to the field. © 2018 National Academy of Sciences. All rights reserved. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/163645
Appears in Collections: 气候变化与战略
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作者单位: Pająk, G., Department of Statistical Physics, Marian Smoluchowski Institute of Physics, Jagiellonian University, Kraków, 30-348, Poland, Faculty of Physics Mathematics, and Computer Science, Tadeusz Kościuszko Cracow University of Technology, Kraków, 30-084, Poland; Longa, L., Department of Statistical Physics, Marian Smoluchowski Institute of Physics, Jagiellonian University, Kraków, 30-348, Poland; Chrzanowska, A., Faculty of Physics Mathematics, and Computer Science, Tadeusz Kościuszko Cracow University of Technology, Kraków, 30-084, Poland
Recommended Citation:
Pająk G.,Longa L.,Chrzanowska A.. Nematic twist-bend phase in an external field[J]. Proceedings of the National Academy of Sciences of the United States of America,2018-01-01,115(44)