Topological transformations of Hopf solitons in chiral ferromagnets and liquid crystals
Topological transformations of Hopf solitons in chiral ferromagnets and liquid crystals
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DOI：
10.1073/pnas.1716887115
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发表时间：
2018-01
期刊：
影响因子：
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通讯作者：
Jung-Shen B. Tai;Paul J. Ackerman;I. Smalyukh
中科院分区：
文献类型：
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作者：
Jung-Shen B. Tai;Paul J. Ackerman;I. Smalyukh
在许多科学的理论中出现的意义，从粒子物理学到凝结物质和宇宙学，稳定的三维拓扑结构在实验上一直难以捉摸，直到最近我们都可以在同一状态之间进行电气和磁性切换。或不同的索引索引。存储设备以及可能为数学结构提供的测试场和新灵感。野外配置通常涉及拓扑结构，尽管奇异线和点缺陷通常是短暂的瞬态状态。在手性nematic和铁磁液体晶体中的非主流孤子结构的磁切换。杆状分子或磁化强度彼此相关。当HopF指数保持不变时，系统可以稳定具有不同HOPF指数的拓扑结构。
Significance While arising in theories in many branches of science, from particle physics to condensed matter and cosmology, stable three-dimensional topological solitons remained experimentally elusive until very recently. We now show that such solitons can be electrically and magnetically switched between states with the same or different Hopf indices. Richness and robustness of this switching promise technological applications in the new breeds of information displays and data storage devices, as well as may provide a test ground and new inspirations for the mathematical knot theory. Liquid crystals are widely known for their facile responses to external fields, which forms a basis of the modern information display technology. However, switching of molecular alignment field configurations typically involves topologically trivial structures, although singular line and point defects often appear as short-lived transient states. Here, we demonstrate electric and magnetic switching of nonsingular solitonic structures in chiral nematic and ferromagnetic liquid crystals. These topological soliton structures are characterized by Hopf indices, integers corresponding to the numbers of times that closed-loop-like spatial regions (dubbed “preimages”) of two different single orientations of rod-like molecules or magnetization are linked with each other. We show that both dielectric and ferromagnetic response of the studied material systems allow for stabilizing a host of topological solitons with different Hopf indices. The field transformations during such switching are continuous when Hopf indices remain unchanged, even when involving transformations of preimages, but discontinuous otherwise.