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

直到最近（2017年）才在严格二维材料中观察到磁性。二维磁有序一直是凝聚态物理学中许多长期问题的核心，特别是关于长程结构、电子和磁有序的存在/缺失，维度对有序/无序转变的影响，以及拓扑结构和固态材料之间的联系。磁性单层最近在诺丁汉大学合成，提供一个实验平台，研究围绕二维物理的理论概念，并开发基于这些材料的新技术。然而，迄今为止，许多这些单层磁性材料尚未在原子尺度上表征。这意味着局部结构和电子无序对全局或宏观磁性的影响尚未确定。这种联系，原子尺度和宏观性质之间的相关性是这个博士学位的主要目标。唯一能够进行这项科学工作的工具是扫描隧道显微镜。它能够在原子尺度上描述结构和电子特性，以及在原子尺度上绘制自旋或磁矩的能力，使其成为该项目的完美工具。诺丁汉大学最近委托了一台能够在磁场中进行测量的低温扫描隧道显微镜，这使得磁性材料的完整表征成为可能。该仪器目前使用液氦冷却，每周消耗约100升，这意味着每年的运营成本约为80，000英镑。Cryogenic设计和制造了这种低温恒温器，并正在开发一种回收和再液化系统来解决这个问题。除了显著降低系统的运营成本外，Cryogenic的净化器还可以让STM连续24/7运行多年，而目前每七天中断一次测量以重新填充冷冻剂。博士学位的重要组成部分该项目将与该公司合作，安装和设计这样一个系统，以尽量减少其对扫描隧道显微镜性能的影响。一个可用的氦收集和再液化设施将为长期使用该工具来研究磁性材料提供改变游戏规则的发展。

Magnetism has only recently (2017) been observed in a strictly two-dimensional material. Magnetic order in two-dimensions has been at the heart of many long-standing queries in condensed matter physics, particularly in relation to the absence /presence of long-range structural, electronic and magnetic order, the influence of dimensionality on order/disorder transition, and the connection between topology and solid-state materials.Magnetic monolayers have recently been synthesised at the University of Nottingham, offering an experimental platform to study both theoretical concepts surrounding two-dimensional physics and develop new technologies built on these materials. Yet, to date, many of these monolayer magnetic materials have not been characterised at the atomic-scale. This means that the impact of local structural and electronic disorder on the global or macroscopic magnetic properties has not yet been established. This connection, a correlation between atomic-scale and macroscopic properties is the primary aim of this Ph.D. studentship.The only tool capable of this scientific endeavour is the scanning tunnelling microscope. Its ability to characterise structural and electronic properties at the atomic-scale, in addition to its ability to map spin or magnetic moments at the atomic-scale, make it the perfect tool for this project. The University of Nottingham has recently commissioned a low-temperature scanning tunnelling microscope capable of measuring in magnetic fields, which enables a complete characterisation of magnetic materials.This instrument is currently cooled with liquid helium and consumes roughly 100 litres per week, this translates to roughly £80,000 per year in operational costs. Cryogenic designed and manufactured this cryostat and is developing a recovery and reliquification system to solve this issue. In addition to significantly reducing the system's operating costs, the liquefier from Cryogenic would allow for continuous 24/7 operation of the STM for years at a time, while measurements are currently disrupted every seven days to refill cryogens. A significant part of the Ph.D. project will be to work with the company to install and design such a system to minimise its impact on the performance of the scanning tunnelling microscope. A working helium collection and reliquification facility will provide a game-changing development for the long-term use of this tool for the investigation of magnetic materials.