Generation, Imaging and Control of Novel Coherent Electronic States in Artificial Ferromagnetic-Superconducting Hybrid Metamaterials and Devices

Condensed matter physicists are constantly looking for interesting new states of matter and new materials with unique exploitable properties which reflect the complex quantum mechanical interactions of the electrons that bind them together. These electronic properties can sometimes be approximated to the sum of individual electrons moving within the material, such as the electrical conduction of electrons in simple metals or semiconductors like silicon. The properties are on the whole more interesting, however, when an accurate description of the material needs to account for the collective and correlated motion of large numbers of electrons. Such collective physics leads to the familiar ferromagnetic properties of materials like iron and, less familiarly, the phenomenon of superconductivity. In the latter electrons are able to flow through the bulk of a superconducting material without generating heat and extraordinarily high electrical currents become possible. This finds application, for example, in the large superconducting magnets required for MRI body scanners. Magnetism and superconductivity are often antagonistic phenomena, since they involve different arrangements of the spins of electrons. Spin is a quantum property of electrons that gives rise to intrinsic magnetic fields - it can be visualised as a tiny compass needle attached to each electron. In ferromagnetism all the spins point in the same direction, but in conventional superconductivity the electrons form pairs (Cooper pairs) in which the spins point in opposite directions. Ferromagnetism therefore normally destroys these Cooper pairs, and hence superconductivity, by causing their spins to align parallel.
Condensed matter physicists often look for new materials where ferromagnetism and superconductivity coexist, since this can suggest the presence of some exotic new form of superconductivity (or other novel quantum state). One example is spin-triplet superconductivity, in which the spins of a Cooper pair prefer to be aligned parallel rather than antiparallel. One way to try and engender such exotic states of matter is to grow artificial materials by depositing very thin superconducting and ferromagnetic films (a few nm thick) on top of one another. In this way the properties of the final structure can be tuned, sometimes leading it to exhibit behaviours that have never been found in naturally occurring bulk materials. An example of this is a unique kind of spin-triplet (so called odd-frequency) superconductivity that has recently been demonstrated in this type of thin film structure. The production of artificial materials can be taken a step further if one also patterns such thin film materials in the plane of the film using advanced electron beam lithography technology, to produce additional patterns and structures on the nanoscale. Such an approach could lead not only to the discovery of interesting new quantum phases, but could also to useful properties that could be exploited in future technologies, such as quantum computing.
In this project we bring together a team of experts with a diverse range of skills that can grow, pattern, measure and undertake theoretical studies on the type of nanostructured materials discussed above. One particularly novel aspect of our approach is the use of powerful imaging techniques involving neutron, muons, X-rays and bespoke scanning magnetic sensors to gain unique insights into both the basic physics at play in systems exhibiting odd-frequency triplet superconductivity as well as the relation between the detailed magnetic and physical structures and their exotic properties. Although the basic aim of this project is the pursuit of new scientific knowledge, we will be looking for interesting effects and properties that might find future applications.

The primary outcome of our research will be the generation of new specialist scientific knowledge. While it is not our intention with this proposal to address directly issues of wealth creation we believe that several aspects of the associated knowledge, techniques and training have wider societal value. The project will employ six post-doctoral researchers and offers a remarkably rich and varied training environment with a high level of PDRA mobility, leading to the development of expertise in a wide range of complementary cutting-edge experimental and theoretical techniques. These include many skills that have direct relevance to industry and commerce e.g. nanolithography and thin film deposition; programming, numerical simulation and modelling; advanced analytical modelling; novel electronics and instrument design. These provide good examples of high-level training and application of the scientific method that are cornerstones of the knowledge-based economy. We will endeavour to provide an appropriate level of skill acquisition and training, in both specialist and generic skills, to support this objective. The skills base is extremely relevant to key areas within the secondary education sector. The provision of high-level training of personnel is thus a key route to wider societal benefit.
While not the prime motivator of this research programme, some of the knowledge we will generate and techniques we will develop have the potential to be directly relevant to areas of high-tech industry. An example of previous engagement with industry is our application of neutron techniques to probe aspects of thin-film magnetic data storage, undertaken in collaboration with major global companies in this area. In the current proposal we extend these and other techniques to new levels of sensitivity which could directly benefit research on, for example, bit patterned media intended for future data storage solutions. Other areas of emerging economic impact that could also benefit from some of the techniques include the layered technology used in organic electronics and photovoltaics, and indeed other groups have begun to adopt similar approaches to measurement in this area. There are also more immediate connections with the field of spintronics where the manipulation of spin as well as charge offers additional degrees of freedom in futuristic electronic devices. The planned research will begin to explore some of the many potential opportunities for integrating superconductivity with spintronics thus helping to establish a UK presence in an area of potential future importance for wealth creation. We note in this context the 2010 European Roadmap on Superconductive Electronics produced by the Fluxonics Society, a society comprising several industrial companies, European government research labs and Universities.
Although this research project is not focused on the generation of IPR nor strong liaisons with industry in this context, we are nonetheless mindful of possibilities to which we will remain receptive and agile. IPR generated as a result of research performed within the project will be covered by a legal Consortium Agreement. Several of us are involved with research projects involving industrial collaborators and sponsors and we are embedded in organisations with a commitment to knowledge exchange. St Andrews for example is a member of the Scottish Universities Physics Alliance (SUPA) that has its own Knowledge Transfer Directorate comprising a full time Director and several Business Development Managers. Both Royal Holloway and ISIS are members of the South East Physics Network (SEPNET), which has outstanding connections to a large number of companies and is strongly engaged in joint PhD programmes, projects and vacation placements. There is thus significant opportunity for exploring issues of wealth creation should they arise, through these and similar arrangements at all the nodes in the project.