Fukuda Jun-Ichi, Nych Andriy, Ognysta Uliana, Žumer Slobodan, Muševič Igor
Department of Physics, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka, 819-0395, Japan.
National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, 305-8568, Japan.
Sci Rep. 2018 Nov 22;8(1):17234. doi: 10.1038/s41598-018-35514-0.
Skyrmions are swirl-like topological entities that have been shown to emerge in various condensed matter systems. Their identification has been carried out in different ways including scattering techniques and real-space observations. Here we show that Kossel diagrams can identify the formation of a hexagonal lattice of half-Skyrmions in a thin film of a chiral liquid crystal, in which case Kossel lines appear as hexagonally arranged circular arcs. Our experimental observations on a hexagonal lattice of half-Skyrmions and other defect structures resembling that of a bulk cholesteric blue phase are perfectly accounted for by numerical calculations and a theoretical argument attributing strong reflections yielding Kossel lines to guided mode resonances in the thin liquid crystal film. Our study demonstrates that a liquid crystal is a model system allowing the investigation of topological entities by various optical means, and also that Kossel techniques are applicable to the investigation of thin systems with non-trivial photonic band structures including topologically protected optical surface states.
斯格明子是一种类似漩涡的拓扑实体，已被证明出现在各种凝聚态物质系统中。它们的识别通过多种方式进行，包括散射技术和实空间观测。在此我们表明，科塞尔图可以识别手性液晶薄膜中半斯格明子六角晶格的形成，在这种情况下，科塞尔线呈现为六边形排列的圆弧。我们对半斯格明子六角晶格以及其他类似于体胆甾相蓝相缺陷结构的实验观测，通过数值计算和理论论证得到了完美解释，该理论将产生科塞尔线的强反射归因于薄液晶薄膜中的导模共振。我们的研究表明，液晶是一个模型系统，能够通过各种光学手段研究拓扑实体，并且科塞尔技术适用于研究具有非平凡光子能带结构的薄系统，包括拓扑保护的光学表面态。
