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

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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.