标题： 拓扑分析与磁性圆柱形纳米线中畴壁变换的实验控制 显示英文标题

标题： Topological analysis and experimental control of transformations of domain walls in magnetic cylindrical nanowires

摘要： 拓扑学是一种强大的工具，用于通过在二维(2D)系统（如薄膜或曲面）和三维体系统中定义拓扑指数来对磁化纹理进行分类。 在新兴的三维纳米磁学领域，必须考虑体积和表面的拓扑数，这需要确定一个适当的全局拓扑不变量以支持分类。 在这里，我们考虑圆柱形纳米线中的畴壁作为三维纳米磁性系统的理想实验场，由电荷电流激发，产生奥斯特场。 我们首先提供了以前未报道的在纳秒时间尺度上发生的畴壁拓扑变换的实验证据。 我们通过微磁模拟研究这些变换，跟踪体积和表面的拓扑特征。我们展示了一个结合这两种特征的拓扑不变量，而在动力学过程中，拓扑电荷从体积到表面发生变化。 当脉冲持续时间与壁的内部变换时间尺度匹配，并且在变换完成前关闭电流时，可以再现实验中的拓扑变化。 我们预计拓扑分类和动态应用适用于任何三维纳米磁性系统。 显示英文摘要

摘要： Topology is a powerful tool for categorizing magnetization textures by defining a topological index in both two-dimensional (2D) systems, such as thin films or curved surfaces, and in 3D bulk systems. In the emerging field of 3D nanomagnetism, both volume and surface topological numbers must be considered, requiring the identification of a proper global topological invariant to support categorization. Here we consider domain walls in cylindrical nanowires as an excellent playground for 3D nanomagnetic systems, excited by a charge current, that generates an OErsted field. We first provide experimental evidence of previously unreported domain-wall transformations of topology occurring at the nanosecond timescale. We investigate these transformations with micromagnetic simulations, tracking both bulk and surface topological signatures.We demonstrate a topological invariant combining both signatures, while the topological charge varies from bulk to surface during the dynamics. The experimental change of topology is reproduced when the pulse duration matches the timescale of the internal transformations of the wall, and the current is switched off before the transformation is complete. We expect that the topological categorization and dynamical exploitation apply to any 3D nanomagnetic system.