A New Paradigm for Quantum Materials Discovery: S = 1/2 Kagome Magnets in the Two-Dimensional Limit

在过去的一个世纪里，材料研究对现代生活产生了惊人的影响。如果没有材料的发现和对固体性质的基本认识的发展，我们就不会有今天我们所依赖的许多先进技术。实现未来技术的一个关键挑战是发现具有从未见过的特性的新型材料，这些材料将突破我们对物理世界的理解的极限，我们可以利用它们来实现社会和经济效益。量子材料和二维材料是新兴材料的两个相关例子，它们可以表现出前所未有的行为。量子材料的性质是由量子力学效应决定的，这种效应在高温和长尺度下仍然很明显。从技术角度来看，量子材料的奇异特性是必不可少的，因为它们将支撑21世纪量子计算等下一代量子技术的发展。同样，最近对二维材料的发现表明，当物质从三维体缩小到原子薄层时，物质会产生非凡的物理特性。石墨烯是一个众所周知的例子，它是一种二维形式的碳，具有出色的导电性、柔韧性和强度，在未来的新型设备应用中具有很大的前景。该提案旨在开发一类新的二维量子材料，将材料化学和凝聚态物理前沿的概念统一起来。特别是，这项研究集中在量子磁体的一种新的化学范式上，这是当前量子材料研究的基石。理论上，量子kagom<s:1>磁体是由角角共享三角形组成的二维阵列，磁矩为S = 1/2，例如，由铜等过渡金属离子的未配对电子产生。这些因素共同产生了与未来先进技术相关的各种令人兴奋的量子力学效应。因此，为了在实验中探索和利用量子磁体的神秘物理特性，实现量子磁体的不同例子是一个关键的材料发现挑战。自2005年一项革命性的材料发现以来，该领域的研究工作主要集中在合成包含量子kagom<s:1>网络的准二维近似的无机材料上。虽然这种方法揭示了一些迷人的材料特性，但它最终受到一个基本需求的限制，即在原子水平上大大提高我们对材料设计的控制，以真正理解量子kagomo<s:1>磁铁固有的实验特征。为了满足这一需求，本研究将首先探索我们控制被称为金属有机框架的磁性混合框架材料家族的组装和后续性能的能力；由无机铜基磁层组成的材料，通过碳基有机分子连接。然后，研究人员将继续研究各种有前途的方法来分层这些材料，并在二维极限下生产出独特的量子kagom<s:1>磁铁。在短期内，该项目将为量子材料的设计和合成提供新的理解，并逐步改变量子磁体的可用化学实现。从长远来看，目标材料的化学性质及其表现非常规物理的强烈倾向可能在从凝聚态理论到磁性测量和器件制造的各个领域产生深远的影响。

Materials research over the past century has had a phenomenal impact on modern-day life. Without materials discovery and the development of a fundamental understanding of the properties of solids, we would lack the many advanced technologies we have come to rely on today. A crucial challenge to enabling the technologies of tomorrow is to discover new classes of materials with never-before-seen properties that push the limits of our understanding of the physical world and that we can harness for societal and economic benefit. Two related examples of emerging classes of materials that can display unprecedented behaviour are quantum materials and two-dimensional materials. Quantum materials are those whose properties are uniquely determined by quantum mechanical effects that remain evident at high temperatures and long length scales. The exotic properties of quantum materials are essential from a technological perspective as they will underpin the development of next-generation quantum technologies, such as quantum computing, over the 21st Century. Equally, the recent discoveries of two-dimensional materials demonstrate the extraordinary physical properties that can arise in matter when downscaled to atomically thin layers from the three-dimensional bulk. A well-known example is graphene, a two-dimensional form of carbon, which displays remarkable conductivity, flexibility and strength, holding great promise for novel device applications in the future. This proposal aims to develop a new class of two-dimensional quantum materials that will unite concepts at the frontiers of materials chemistry and condensed matter physics. In particular, this study centres on a novel chemical paradigm for the quantum kagomé magnet, a cornerstone of current quantum materials research. In theory, the quantum kagomé magnet is a two-dimensional array of corner-sharing triangles of S = 1/2 magnetic moments that arise, for example, from the unpaired electrons of a transition metal ion such as copper. These ingredients conspire to give rise to an exciting assortment of quantum mechanical effects pertinent to future advanced technologies. As such, the realisation of different examples of quantum kagomé magnets is a crucial materials discovery challenge in order to explore and exploit their enigmatic physical properties experimentally. Since a revolutionary materials discovery in 2005, the research effort in this field has focussed heavily on the synthesis of inorganic materials which contain quasi-two-dimensional approximations of a quantum kagomé network. While this approach has unveiled some fascinating materials properties, it is ultimately limited by a fundamental need to vastly improve our control of materials design at the atomic level to truly understand the experimental signatures intrinsic to the quantum kagomé magnet. To address this need, this research will first explore our ability to control the assembly and ensuing properties of a family of magnetic hybrid framework materials known as metal-organic frameworks; materials composed of inorganic copper-based magnetic kagomé layers connected via carbon-based organic molecules. The research will then go on to investigate a variety of promising routes to delaminate these materials and produce unique realisations of the quantum kagomé magnet in the two-dimensional limit. In the short-term, this project will deliver new understanding in quantum materials design and synthesis and a step-change in the available chemical realisations of quantum kagomé magnets. In the longer-term, the chemical nature of the targeted materials coupled with their strong propensity to manifest unconventional physics may have far-reaching implications in diverse fields, from condensed matter theory to magnetic property measurement and device fabrication.