Strain-tuning electronic structure and quantum many-body interactions

Quantum Materials represent a frontier research endeavour. The strong interactions at the heart of their exotic physical properties has made understanding, let alone predicting, their materials properties one of the most profound challenges of modern-day solid state physics and materials chemistry. This problem is not just an intellectual curiosity, however; harnessing control over the collective states that these systems can host, such as superconductivity, metal-insulator transitions, and magnetic orderings, could open new routes to designing fast, energy-efficient, and smart multifunctional technologies, operating using completely different design principles to the Silicon-based logic of today.

To progress towards an improved fundamental understanding, and thereby ultimate exploitation, of these systems requires controlled, new, experimental approaches. Here, we propose to develop new capabilities for applying large, reversible, and continuously-tuneable uniaxial pressures in conjunction with angle-resolved photoemission experiments. This promises novel insight into how the electronic structures and many-body interactions of quantum materials evolve when subjected to a particularly clean tuning parameter, which is of fundamental importance to further our understanding of the quantum many-body problem in solids. To this end, we will focus on two key materials systems, the metallic transition-metal dichalcogenides and the layered ruthenate oxides. These are each of enormous current interest in their own right, as potential hosts of topological excitations, as new 2D materials candidates, and as unconventional magnets, and are chosen here to provide important complementary insights into the nature of phase competition, electron-lattice interactions, and strong electronic correlations in solids.

The programme of work proposed here will develop bespoke new scientific instrumentation, and will utilise this to study questions of fundamental importance in our understanding of the quantum many-body problem in solids. In turn, this will help to provide the foundational underpinnings that will be necessary to exploit quantum materials in a new generation of high-speed, highly-efficient, and multi-functional technologies in the future.

***Knowledge creation***
One of the primary impacts of this work is thus the creation of knowledge. We aim to develop novel routes to tune the quantum many-body states of solids, and to probe these with unprecedented precision. This promises fundamental new insights into the nature of electronic correlations in solids, and how these respond to the application of external pressure.

***Economic impact***
Although the research topic is fundamental in nature, the development of bespoke scientific instrumentation nonetheless presents opportunities for commercialisation of specialist apparatus in the shorter term. On longer timescales, the fundamental insights gained on the control of many-body interactions in solids will help deepen the underpinning body of knowledge that is required to achieve ultimate exploitation of quantum materials. Quantum Materials are truly Advanced Materials. Their giant responses to external stimuli and their multi-functional properties could present enormous opportunities for disruptive technologies of the future, but progress at present is limited by a lack of fundamental understanding of these materials as well as an inability to deterministically achieve desired functional properties. The research programme seeks to make advances in both of these areas, and thus is well aligned with Advanced Materials-related goals of the UK Industrial Strategy, and of Innovate UK priorities to develop 'More than Moore' technologies

***People***
The project will provide education and training for a dedicated postdoctoral researcher, as well as three associated research students. The varied aspects of this work will ensure that they gain a thorough training in a range of technical, analytical, and transferrable skills. This will in turn provide a springboard for them to excel in careers either in academia or in various high-tech industrial sectors, leaving them well placed to become future leaders in their chosen fields.

***Society***
To engage, excite, and educate the public about the importance of scientific research in general, and controlling Quantum Materials in particular, we will undertake public engagement activities related to the broad topic of the proposed research. This is of general societal importance, and also an important responsibility to help encourage more people into STEM subjects in the future. It, in turn, will help to drive enhanced policy informed by increased understanding, as well as helping to maintain the critical people pipeline of highly-skilled workers necessary to deliver and support a high-tech economy in the UK.