近日，荷兰阿姆斯特丹大学的Corentin Coulais及其研究团队取得一项新进展。经过不懈努力，他们对有源超材料中的非互易拓扑孤子进行研究。相关研究成果发表已于2024年3月20日在国际知名学术期刊《自然》上发表。

该研究团队引入了一种局部驱动机制，使孤子和反孤子在同一方向上加速: 非互易驱动。为了实现这一机制，研究人员构建了一种由双稳态势下非互易耦合谐振子组成的有源机械超材料。研究人员发现这样的非线性将非互易激励——所谓的非厄米皮肤波，通常是不稳定的——诱导成鲁棒的单向(反)孤子。研究人员利用这种非互易的拓扑孤子，构建了一个能够传输和过滤单向信息的有源波导。最后，他们在另一类超材料中说明了这一机制，表明“超对称”的破坏只会导致反孤子被驱动。

这一观察和模型证实非互易性和拓扑孤子之间的微妙相互作用，即孤子通过局部拉伸材料来产生自己的驱动力。在本文研究范围之外，非互易孤子可能为机器人运动提供一种有效的驱动机制，并可能出现在其他环境中，例如量子力学、光学和软物质。

据悉，从蛋白质基序到黑洞，拓扑孤子是普遍的非线性激励，具有鲁棒性，可以由外场驱动。迄今为止，现有的驱动机制都是朝着相反的方向加速孤子和反孤子。

附：英文原文

Title: Non-reciprocal topological solitons in active metamaterials

Author: Veenstra, Jonas, Gamayun, Oleksandr, Guo, Xiaofei, Sarvi, Anahita, Meinersen, Chris Ventura, Coulais, Corentin

Issue&Volume: 2024-03-20

Abstract: From protein motifs to black holes, topological solitons are pervasive nonlinear excitations that are robust and can be driven by external fields. So far, existing driving mechanisms all accelerate solitons and antisolitons in opposite directions. Here we introduce a local driving mechanism for solitons that accelerates both solitons and antisolitons in the same direction instead: non-reciprocal driving. To realize this mechanism, we construct an active mechanical metamaterial consisting of non-reciprocally coupled oscillators subject to a bistable potential. We find that such nonlinearity coaxes non-reciprocal excitations—so-called non-Hermitian skin waves, which are typically unstable—into robust one-way (anti)solitons. We harness such non-reciprocal topological solitons by constructing an active waveguide capable of transmitting and filtering unidirectional information. Finally, we illustrate this mechanism in another class of metamaterials that shows the breaking of ‘supersymmetry’ causing only antisolitons to be driven. Our observations and models demonstrate a subtle interplay between non-reciprocity and topological solitons, whereby solitons create their own driving force by locally straining the material. Beyond the scope of our study, non-reciprocal solitons might provide an efficient driving mechanism for robotic locomotion and could emerge in other settings, for example, quantum mechanics, optics and soft matter.

DOI: 10.1038/s41586-024-07097-6

Source: https://www.nature.com/articles/s41586-024-07097-6