Tai Jung-Shen B, Wu Jin-Sheng, Smalyukh Ivan I
Department of Physics and Chemical Physics Program, University of Colorado, Boulder, CO, 80309, USA.
Department of Electrical, Computer, and Energy Engineering, Materials Science and Engineering Program and Soft Materials Research Center, University of Colorado, Boulder, CO, 80309, USA.
Nat Commun. 2022 May 27;13(1):2986. doi: 10.1038/s41467-022-30494-2.
Arising in many branches of physics, Hopf solitons are three-dimensional particle-like field distortions with nontrivial topology described by the Hopf map. Despite their recent discovery in colloids and liquid crystals, the requirement of applied fields or confinement for stability impedes their utility in technological applications. Here we demonstrate stable Hopf solitons in a liquid crystal material without these requirements as a result of enhanced stability by tuning anisotropy of parameters that describe energetic costs of different gradient components in the molecular alignment field. Nevertheless, electric fields allow for inter-transformation of Hopf solitons between different geometric embodiments, as well as for their three-dimensional hopping-like dynamics in response to electric pulses. Numerical modelling reproduces both the equilibrium structure and topology-preserving out-of-equilibrium evolution of the soliton during switching and motions. Our findings may enable myriads of solitonic condensed matter phases and active matter systems, as well as their technological applications.
霍普夫孤子出现在物理学的许多分支中，是具有由霍普夫映射描述的非平凡拓扑结构的三维类粒子场畸变。尽管它们最近在胶体和液晶中被发现，但稳定性需要外加场或限制条件，这阻碍了它们在技术应用中的实用性。在这里，我们展示了一种液晶材料中的稳定霍普夫孤子，由于通过调整描述分子排列场中不同梯度分量能量成本的参数的各向异性来增强稳定性，所以不需要这些条件。然而，电场允许霍普夫孤子在不同几何形态之间相互转换，以及响应电脉冲的三维跳跃式动力学。数值模拟再现了孤子在切换和运动过程中的平衡结构以及拓扑保持的非平衡演化。我们的发现可能会促成无数的孤子凝聚态相和活性物质系统及其技术应用。
