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

直到最近(2017)才在严格的二维材料中观察到磁性。二维磁有序是凝聚态物理中许多长期存在的问题的核心，特别是关于长程结构、电子和磁性有序的不存在，维度对有序/无序转变的影响，以及拓扑和固态材料之间的联系。诺丁汉大学最近合成了磁性单分子膜，为研究围绕二维物理的理论概念和开发建立在这些材料上的新技术提供了一个实验平台。然而，到目前为止，许多这种单层磁性材料还没有在原子尺度上进行表征。这意味着局域结构和电子无序对整体或宏观磁性的影响尚未确定。与此相关，原子尺度和宏观性质之间的相关性是这一博士生的主要目标。唯一能够进行这一科学努力的工具是扫描隧道显微镜。它能够在原子尺度上表征结构和电子性质，此外还能够在原子尺度上绘制自旋或磁矩图，使其成为这一项目的完美工具。诺丁汉大学最近委托制作了一台能够在磁场中测量的低温扫描隧道显微镜，这使得能够对磁性材料进行完整的表征。该仪器目前使用液氦制冷，每周消耗约100升，这相当于每年约80,000 GB的运营成本。低温公司设计和制造了这个低温恒温器，并正在开发一种回收和再供应系统来解决这个问题。除了显著降低系统的运营成本外，低温液化器还将允许STM一次连续24/7运行数年，而目前每七天就会中断一次测量，以补充冷冻机。博士项目的一个重要部分将是与该公司合作安装和设计这样一个系统，以将其对扫描隧道显微镜性能的影响降至最低。一个正在运行的氦收集和再矿化设施将为长期使用这一工具调查磁性材料提供一个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.