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Blue Phase III: Topological Fluid of Skyrmions
Physical Review X ( IF 12.5 ) Pub Date : 2022-01-05 , DOI: 10.1103/physrevx.12.011003
J. Pišljar , S. Ghosh , S. Turlapati , N. V. S. Rao , M. Škarabot , A. Mertelj , A. Petelin , A. Nych , M. Marinčič , A. Pusovnik , M. Ravnik , I. Muševič

Skyrmions are topologically protected, vortexlike formations of a field that cannot be removed by any smooth transformation and emerge in a range of fundamentally different, either quantum or classical systems, from spin textures to chiral ferromagnets and chiral complex fluids. Notably, they are generally observed in thin ordered or disordered quasi-2D layers, but little is known about their three-dimensional structuring and organization, including structural transitions from 2D to 3D. Here, we show experimentally and numerically that the blue phase (BP) III of a chiral liquid crystal is a 3D fluid of chiral skyrmion filaments of the nematic orientational field, entangled with a 3D network of topological defect lines. It is an effective 3D dynamic fluid determined by the thermal fluctuations of two distinct branches of excitations: rapid internal fluctuations of the skyrmion structure and a slow collective motion of the skyrmion filaments. When confined to less than an approximately 150-nm layer, the 3D bulk skyrmion fluid transforms into a different effectively 2D liquid of half-skyrmions, with the dynamics of the skyrmion liquid slowing down by an order of magnitude and with the individual skyrmions lingering, and even disappearing into, and reappearing from the homogeneous liquid crystal. The thickness-temperature phase diagram actually shows that both the BPIII and BPI phases are made of skyrmions, which when confined to less than approximately 150 nm cells transform equally into a 2D half-skyrmion liquid. The temperature range of this 2D half-skyrmion liquid is much broader than the temperature interval of BP phases, which makes BP materials interesting for broad-temperature-range skyrmionic applications. We envisage a soft matter skyrmionic device, in which skyrmions are created and detected by light.

中文翻译:

蓝相 III:Skyrmions 的拓扑流体

Skyrmions 是受拓扑保护的涡旋状场,无法通过任何平滑变换去除,并出现在一系列根本不同的量子或经典系统中,从自旋纹理到手性铁磁体和手性复合流体。值得注意的是,它们通常在薄有序或无序的准二维层中观察到,但对其三维结构和组织知之甚少,包括从 2D 到 3D 的结构转变。在这里,我们通过实验和数值显示,手性液晶的蓝相 (BP) III 是向列取向场的手性斯格明子丝的 3D 流体,与拓扑缺陷线的 3D 网络纠缠在一起。它是一种有效的 3D 动态流体,由两个不同激发分支的热波动决定:斯格明子结构的快速内部波动和斯格明子细丝的缓慢集体运动。当限制在大约 150 nm 层以内时,3D 大块的斯格明子流体转变为半斯格明子的不同有效 2D 液体,斯格明子液体的动力学减慢一个数量级,并且单个斯格明子挥之不去,甚至在均质液晶中消失,再出现。厚度-温度相图实际上显示 BPIII 和 BPI 相均由斯格明子组成,当限制在小于约 150 nm 的细胞中时,它们同样转化为二维半斯格明子液体。这种二维半斯格明子液体的温度范围比 BP 相的温度区间宽得多,这使得 BP 材料对宽温度范围的斯格米离子应用很有吸引力。我们设想了一种软物质 Skyrmionic 设备,其中 Skyrmions 是由光产生和检测的。
更新日期:2022-01-06
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