Engineering and imaging enhanced spin splittings in solids

An important emerging field in condensed-matter physics is spintronics, a variant of electronics exploiting the electron's spin. While this concept underpins the dramatic improvements in magnetic storage technology seen over the last two decades, active electronic devices such as spin-based transistors have proved much more elusive. A key challenge is to create a large spin splitting of the underlying electronic states of materials, a pre-requisite to their use for spintronic devices operating at room temperature and having small spatial dimensions. Moreover, this spin splitting must be electrically controllable to achieve switching in a device. Together, this would not only promise a route to fast and energy-efficient electronics, but would open unique possibilities for achieving coherent manipulation of electron spins for solid-state quantum devices.

We will undertake a series of three complementary pilot studies aimed at identifying new approaches to stabilise spin splittings that are large compared to room temperature and that are tuneable using simple external control. We will build up a microscopic picture of how spin splitting can be created and manipulated in promising chalcogen and halide-based compounds, using advanced electron spectroscopy to directly visualise their electronic structure and probe how it can be tuned to maximise the effects of spin-orbit coupling. We will seek to disentangle the interconnected roles of multiple atomic orbitals, coupled real and momentum-space spin-orbital textures, and topological band structure properties. Through this, we will not only generate new fundamental understanding, but also develop novel combined methodologies for engineering spin splittings orders of magnitude larger than have been achieved in conventional semiconductor-based systems to date. The project is supported by partners from the UK and Japan, brining complementary expertise and capability in materials synthesis and theoretical modeling. It will utilise unique laboratory infrastructure in the UK as well as key national facilities to advance new levels of control over spin splitting in solids, providing a materials approach to underpin future quantum technologies.

The programme of work proposed here aims to identify novel approaches of electronic structure engineering to move beyond the current state-of-the-art approaches to semiconductor-based spintronics, unveiling new materials and design principles for stabilising large tuneable spin splittings in solids.

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Potential commercial beneficiaries
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This has the ultimate potential to provide a disruptive impact on current technological sectors, particularly within computing and communication (see also "Pathways to Impact"). Most directly relevant are:
i) New possibilities for nanoscale spintronic devices such as the spin transistor, an area actively investigated by leading technology companies with significant UK presence such as Toshiba, Hitachi, IBM;
ii) A solid-state materials approach underpinning future quantum technologies, [e.g. addressing spin-based qubits for use in quantum computing and communication], of interest to high-tech companies such as IBM and Microsoft;
iii) Understanding of new advanced materials, widely recognised as a key enabling technology (KET) and strategic priority by BIS and the Technology Strategy Board [e.g. TSB strategy 2012-2015; Eight Great Technologies - David Willetts]. The European Commission has estimated KETs to form a global market worth 1 trillion euros by 2015 (http://ec.europa.eu/enterprise/sectors/ict/ key_technologies/index_en.htm). Those studied here will have potential electronic, computing, and energy applications.

Added value for performing this research in the UK is ensured by:
i) The UK electronics sector is one of the largest in the world, with over 8000 companies generating an annual revenue of around £29 billion [source: TSB strategy 2012-2015];
ii) Leading industry-linked research labs based in the UK (e.g. Hitachi and Toshiba). As such, we are well placed to transition arising IPR and research advances through to near-market applications;
iii) Spintronics and quantum-based electronics promise to be a leading contender for post-CMOS (Complementary Metal Oxide Semiconductor) device applications, as brought to prominence, for example, by the recent £270M investment in quantum technologies by EPSRC. New advances in materials and understanding of the physics of these systems promise enormous possibility for growth of this sector, with high-performance and energy efficient devices the ultimate application of the proposed research (e.g. spin-polarised electron sources and injectors, spin field effect transistors, solid state spin qubit schemes).

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Training future research and industry leaders
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The project will provide a strong education and training for a dedicated PDRA as well as two associated research students (already in place). Participating in the varied aspects of this work will gain them a solid understanding of electronic structure measurements and theory, and more broadly solving challenging scientific problems, benefiting them for possible future research-based careers. Moreover, they will profit from technical and transferrable skills-training (detailed in the pathways to impact) leaving them well placed to become future industry leaders, for example within the electronics and spintronics-based high-tech sectors.