Hough L E, Jung H T, Krüerke D, Heberling M S, Nakata M, Jones C D, Chen D, Link D R, Zasadzinski J, Heppke G, Rabe J P, Stocker W, Körblova E, Walba D M, Glaser M A, Clark N A
Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, CO 80309, USA.
Science. 2009 Jul 24;325(5939):456-60. doi: 10.1126/science.1170027.
In the formation of chiral crystals, the tendency for twist in the orientation of neighboring molecules is incompatible with ordering into a lattice: Twist is expelled from planar layers at the expense of local strain. We report the ordered state of a neat material in which a local chiral structure is expressed as twisted layers, a state made possible by spatial limitation of layering to a periodic array of nanoscale filaments. Although made of achiral molecules, the layers in these filaments are twisted and rigorously homochiral--a broken symmetry. The precise structural definition achieved in filament self-assembly enables collective organization into arrays in which an additional broken symmetry--the appearance of macroscopic coherence of the filament twist--produces a liquid crystal phase of helically precessing layers.
在手性晶体的形成过程中，相邻分子取向发生扭曲的趋势与有序排列成晶格的要求不相容：扭曲会从平面层中被排除，代价是产生局部应变。我们报道了一种纯物质的有序状态，其中局部手性结构表现为扭曲层，这种状态是通过将分层在空间上限制为纳米级细丝的周期性阵列而实现的。尽管这些细丝由非手性分子构成，但其层是扭曲的且严格同手性——这是一种对称性破缺。细丝自组装过程中实现的精确结构定义使得能够集体组织成阵列，其中另一种对称性破缺——细丝扭曲宏观相干性的出现——产生了螺旋进动层的液晶相。
