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了解的发展，我们就不会缺乏我们今天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前所未有的性能的新材料类别，这些材料突破了我们对物理世界的理解极限，我们可以利用这些材料来获得社会和经济效益。可以显示出前所未有的行为的新兴材料类别的两个相关例子是量子材料和二维材料。量子材料是那些其性质唯一地由量子力学效应决定的材料，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，因为它们将为21世纪量子计算等下一代量子技术的发展奠定基础。同样，最近对二维材料的发现表明，当物质从三维物质缩小到原子薄层时，物质可以产生非凡的物理性质。一个著名的例子是石墨烯，这是一种碳的二维形式，它表现出非凡的导电性、灵活性和强度，在未来的新设备应用中有着巨大的前景。这项提议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的前沿概念统一起来。特别是，这项研究集中在量子Kagomé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Kagomé磁体是一个角共享三角形的二维阵列，这些三角形的角共享三角形的S=1/2的磁矩，例如，来自铜等过渡金属离子的未配对电子。这些成分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，实现不同的量子Kagomé磁体是一项关键的材料发现挑战，以便通过实验探索和利用它们神秘的物理特性。自从2005年材料的革命性发现以来，这一领域的研究主要集中在无机材料的合成上，这些材料包含了量子kagomé网络的准二维近似。虽然这种方法揭示了一些令人着迷的材料特性，但它最终受到一个基本需求的限制，即极大地改善我们在原子水平上对材料设计的控制，以真正理解量子Kagomé磁铁固有的实验签名。为了满足这一需求，这项研究将首先探索我们控制磁性杂化骨架材料家族的组装和随之而来的性能的能力，这些材料被称为金属-有机骨架，这些材料由无机铜基磁性Kagomé层组成，通过碳基有机分子连接。然后，这项研究将继续研究各种有希望的方法来将这些材料分层，并在二维极限下产生独特的量子Kagomé磁铁实现。在短期内，该项目将在量子材料设计和合成方面带来新的理解，并在量子Kagomé磁体的现有化学实现方面取得阶段性变化。从长远来看，目标材料的化学性质，再加上它们表现出非常规物理的强烈倾向，可能会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.