Observing, Creating and Addressing Topological Spin Textures in a Monolayer XY Magnet

在20世纪70年代早期的一系列开创性工作中，John Kosterlitz和David Thouless首次将拓扑学概念与固体物理学联系起来。这个框架的基础是离散拓扑单元，一个由其平滑变形成连续背景的阻力定义的对象，就像磁盘不能平滑变形成环或环面一样。Kosterlitz和Thouless表明，他们所探索的系统的最有利构型必须包含这些拓扑单元。然后，他们在这些物体的基础上预测了一种没有对称性破坏的物质相变，这违反了当时所有已知的理论和观察结果。这种所谓的拓扑相变后来被用来描述薄膜超导体、液晶和二维磁体中的相变。由于这项工作，Kosterlitz和Thouless共同获得了2016年诺贝尔奖。然而，尽管这些发现具有开创性的性质，并得到了随后广泛的实验支持，但最初预测的拓扑单元从未在单个单元水平上被观察到。在这项工作计划中，我们将首次使用高度先进的显微镜技术来“看到”这些拓扑对象中的每一个。这些显微镜无与伦比的分辨率可以进一步用于绘制物体的内部，一直到它们的原子构成单元。当这些实验与Kosterlitz和Thouless考虑的原始问题的先进计算方法相结合时，将为这些拓扑保护对象提供一个全新的微观肖像。然而，这项工作的目的远远超出了简单地观察拓扑单元；我们将开发并提供一系列方法来主动操作这些对象。第一套操作技术将利用显微镜本身的影响，就像放大镜可以用来生火一样。第二系列的方法将修改周围的环境，以影响拓扑对象的性质和行为。由于单个拓扑单元不能平滑变形，这为信息技术提供了前所未有的机会：利用拓扑状态来存储和保护一条信息。拓扑保护数据避开了基于能量的传统方法来保护信息，使它们非常有希望用于高密度、节能的磁信息技术方法。最终，提出的实验集旨在告诉我们如何从微观拓扑元素向计算机的全功能单元移动。在此过程中获得的见解将回答许多更基本的问题：拓扑在多大程度上保护信息？这些装置在真实的，有缺陷的材料中表现如何？我们可以采取什么方法来影响这些物体的基本行为？

In a series of pioneering works in the early 1970's, John Kosterlitz and David Thouless first connected the concept of topology to the physics of solids. The basis of this framework is the discrete topological unit, an object defined by its resistance to being smoothly deformed into a continuous background, in the way a disk cannot be smoothly deformed into a ring or torus. Kosterlitz and Thouless showed that the most favourable configurations of the systems they explored must host these topological units. They then went on to predict a material phase transition without symmetry breaking based on these objects, violating all known theories and observations at the time. This so-called topological phase transition has subsequently been used to describe transitions in thin-film superconductors, liquid crystals, and two-dimensional magnets. For this work, Kosterlitz and Thouless shared the 2016 Nobel Prize. Yet, despite the groundbreaking nature of these findings and their subsequent wide-ranging experimental support, the topological units originally predicted have never been observed at the single unit level. In this programme of work, we will use highly advanced microscopy techniques to "see" each of these topological objects for the first time. The unparalleled resolution of these microscopes can be further used to map the interior of the objects all the way down to their atomic building blocks. These experiments, when combined with advanced computational approaches to the original problem considered by Kosterlitz and Thouless, will provide an entirely new microscopic portrait of these topologically protected objects.Yet, this work aims far beyond simply observing the topological units; we will develop and deliver a series of approaches to actively manipulate these objects. The first set of techniques for manipulation will utilize influence from the microscope itself, in much the same way a magnifying glass can be used to start a fire. The second series of approaches will modify the surrounding environment to influence the properties and behaviour of the topological objects. As an individual topological unit cannot be smoothly deformed, it represents an unprecedented opportunity for information technology: using a topological state to store and protect a piece of information. Topologically protected data sidesteps the conventional approaches based on energy to protect information, making them extremely promising for high-density, energy efficient approaches to magnetic information technologies.Ultimately, the set of experiments proposed is designed to inform how we might move from a microscopic topological element toward a fully functional unit of a computer. The insights picked up along the way will answer many more fundamental questions: To what extent does topology protect information? How do these units behave in real, that is defective, materials? What approaches can we take to influence the fundamental behaviour of these objects?