Quantum Dynamics in Correlated Spin Systems

与我们的自然认知相反，依赖于量子特性的材料和设备在我们的日常生活中扮演着不可或缺的角色。即使是看似平凡的现象，如导电，也依赖于带隙图，而带隙图本质上是量子力学的；实际上，这是一个理论模型，它描述了为什么，例如，铜是金属，硅是半导体，可以使用电子与它们所在的晶格相互作用的量子力学来构建。这一图景的延伸导致了对一些超导体的解释，超导体是一种不带任何电阻地导电的材料。虽然超导体最初在1911年被发现时是人们最感兴趣的东西，但最近它已经成为医院核磁共振扫描仪功能的基础。虽然从发现、基本实验和兴趣到商业应用的时间线很长，但这通常是社会范式转换技术的途径。这种研究物质基本性质的方法仍然具有很高的相关性，实际上，量子拓扑材料在今天是普遍感兴趣的。大多数器件都是在微米级制造的，但通常需要对母体材料有充分的了解，才能设计和控制所使用的材料。这一提议牢牢地植根于前沿科学领域，并将利用调查小组开发的新技术在基础水平上调整和理解量子相互作用。该项目是基于一种名为自旋冰的材料。这种材料的美妙之处在于，之前的研究已经确定了人们熟知的基本的、显然是经典的特性。我们想要更进一步地研究和描述涌现状态，其中的性质可以通过改变实验变量和迄今被忽视的量子动力学的影响来操纵，而量子动力学的作用低于观察到的物理行为。这一提议利用了我们对自旋冰经典性质的现有知识，并将研究潜在的量子过程。特别是，我们将研究自旋冰的所谓磁单极子的量子隧穿。这将让我们了解未来如何调整量子态。在相关自旋物理学中，一个明确的目标是理解经典行为和量子行为之间的交叉。在这个提议中，我们将研究自旋冰，它具有非常大的磁矩，通常被描述为经典磁铁，以揭示潜在的量子行为。我们已经确定了几种方法来探索这一点，重要的是，所有方法都需要我们在过去几年开发的独特的高频磁感仪。我们已经确定稀自旋冰是一种研究磁化隧穿的材料，并建议研究相图作为磁场的函数。这将使我们能够理解这种材料中的磁单极子在低温下是如何跳跃的，以及出现态和非平衡态是如何发展的。此外，我们还可以调整施加在自旋冰上的磁场，以寻找量子涨落可能起重要作用的临界点。我们还可以观察单极在新的自旋冰材料中以比以前可能的更高的频率隧穿。这笔赠款将使我们能够开发和保留高水平的技术和科学专门知识，并培养未来发展尖端科学技术的科学领导者。

Contrary to our natural perceptions materials and devices which rely on quantum properties play an integral role in our everyday life. Even seemingly mundane phenomena such as electrical conduction relies on the band gap picture which is fundamentally quantum mechanical in nature; indeed a theoretical model which describes why, for example, copper is a metal, and silicon a semiconductor can be constructed using the quantum mechanics of electrons interacting with the crystal lattice upon which they sit. Extensions of this picture have led to the explanation of some superconductors, materials which conduct electricity without any resistance. Superconductors, although initially of fundamental interest at the time of their discovery in 1911, have more recently underpinned the function of MRI scanners in hospitals. Although the timelines from discovery, fundamental experimentation and interest to commercial applications are long, this has generally been the pathway to paradigm shifting technologies for society.This methodology of investigating fundamental properties of matter remain highly relevant and indeed, quantum topological materials are of general interest today. Most devices are fabricated in the micro-metre regime, but a full understanding of the parent bulk material is generally required to design and control the materials used. This proposal is firmly based in the realm of frontier science, and will exploit new techniques that have been developed by the investigation team to tune and understand quantum interactions at a fundamental level. The project is based upon a material known as spin ice. The beauty of this material is that previous research has identified the basic, apparently classical, properties that are well-understood. We want to go further to investigate and characterise emergent states, where properties can be manipulated by changing experimental variables and the effect of hitherto neglected quantum dynamics that underly the observed physical behaviour. This proposal exploits our existing knowledge of the classical properties of spin ice and will investigate underlying quantum processes. In particular we will study the quantum tunneling of spin ice's so-called magnetic monopoles. This will allow us to understand how to tune quantum states in the future. In correlated spin physics a clear goal has been to understand the crossover between classical and quantum behaviour. In this proposal we will investigate spin ice which has a very large magnetic moment and has often been described as a classical magnet, to reveal underlying quantum behaviour. We have identified several methods to explore this, and importantly all require our unique high frequency susceptometer that we have developed over the past few years. We have already identified dilute spin ice as a material to investigate tunneling of the magnetisation and propose to investigate the phase diagram as a function of magnetic field. This will allow us to understand how magnetic monopoles hop at low temperatures in this material, and how the emergent and non-equilibrium states develop. Moreover we can tune a magnetic field applied to spin ice to look at a critical point where quantum fluctuations may play a significant role. We can also look at the tunneling of monopoles in new spin ice materials at higher frequency than previously possible. This grant will allow us to develop and retain high-level technical and scientific expertise and train a future scientific leader in developing cutting-edge science and technology.