发表机构
Laue-Langevin Institute; Landau Institute for Theoretical Physics, RAS（劳厄-朗之万研究所; 俄罗斯科学院列夫·朗道理论物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文用Landau理论解释液晶中扭曲-弯曲相纳米螺旋结构的涌现，源于短程取向序参量凝聚，类比de Gennes理论，预测弱一级相变及新Goldstone模式。
AI 中文摘要
由弯曲核和二聚体分子组成的液晶中扭曲-弯曲向列相的发现，揭示了软凝聚态物质中纳米尺度周期结构自发形成的一种意外机制。与常规液晶相不同，扭曲-弯曲相在缺乏分子手性的情况下表现出纳米尺度的螺旋状调制。在这篇献给已故的R. Meyer的笔记中，我们讨论了这一现象的Landau唯象解释。核心思想是，一个短程取向序参量发生凝聚，从而产生具有有限波矢的螺旋状结构。我们强调，常规向列序已经是长程的，而额外的序参量描述了隐藏在向列态内部的局部取向关联。由此产生的相变与de Gennes关于向列-近晶A相变的理论具有密切的类比。涨落效应预计会使该相变变为弱一级相变。该理论还预测了一种与螺旋状状态的自发破缺连续对称性相关联的新Goldstone模式。
英文摘要
The discovery of the twist-bend nematic phase in liquid crystals composed of bent-core and dimeric molecules has revealed an unexpected mechanism for the spontaneous formation of nanoscale periodic structures in soft condensed matter. Unlike conventional liquid-crystalline phases, the twist-bend phase exhibits a nanoscale heliconical modulation despite the absence of molecular chirality. In this note, dedicated to the late R. Meyer, we discuss a Landau phenomenological interpretation of this phenomenon. The central idea is that a short-range orientational order parameter undergoes condensation, giving rise to a heliconical structure characterized by a finite wave vector. We emphasize that the conventional nematic order is already long-ranged, whereas the additional order parameter describes local orientational correlations hidden within the nematic state. The resulting phase transition bears a close analogy to the de Gennes theory of the nematic--smectic-A transition. Fluctuation effects are expected to drive the transition weakly first order. The theory also predicts a new Goldstone mode associated with the spontaneously broken continuous symmetry of the heliconical state
Comments6 pages
