International network to explore novel superconductivity at advanced oxide superconductor/magnet interfaces and in nanodevices

Lead Research Organisation: University of Cambridge
Department Name: Materials Science & Metallurgy

Abstract

This International Network of world-leading experimental and theoretical groups in Japan, South Korea, Italy and the UK will lead a programme to explore novel superconductivity at oxide superconductor interfaces with magnetic materials and in nanodevices. Through a better understanding of materials properties and processing, our vision is to realise full control over superconducting symmetry at oxide interfaces and to setup Cambridge and Kyoto as a global hubs to explore the science of advanced oxide interfaces and unconventional superconductivity.
The past decade has seen rapid developments in the understanding of unconventional superconductivity at the interface between conventional (s-wave) superconductors and ferromagnets [Nature Physics 11, 307 (2015)]. A highlight was the experimental demonstration of a triplet proximity effect by the UK applicants [Science 329, 59 (2010)], which required the transformation of spin-singlet Cooper pairs by a spin-mixing interface into spin-triplet pairs. Another example is a possible creation of electron-composite particle-antiparticles in nanowire/superconductor devices. Such Majorana Fermions are also expected in a half-quantum flux state of a spin-triplet superconductor, and the Japanese core member (Maeno) obtained the first evidence for this using superconducting micro-rings [Science 311, 186 (2011)].

In parallel, the understanding of unconventional superconductivity in superfluid helium and in compounds such as Sr2RuO4 (SRO) [e.g. Science 331, 186-188 (2011) and Science 344, 283 (2014)] has also seen dramatic advances. The triplet (p-wave) state in SRO is even-frequency and is conceptually different to the odd-frequency triplet pairing induced in ferromagnets on s-wave superconductors. However, there are theoretical predictions that alternative pairing states can be induced at surfaces, which raise the prospect of coupling different superconducting states via interface-engineered proximity effects between SRO and conventional superconductors. One of the key aims of the Network is to investigate the coupling of different superconducting symmetries taking SRO and ferromagnet/superconductor structures as a model system. There are theoretical predictions that the surface of SRO and ferromagnet/superconductor hybrids can support an induced odd-frequency triplet-state and so there should be a proximity effect from the conventional superconductor which would create or enhance the superconductivity in a SRO crystal or thin-film. Achieving this will enable detailed studies of the electron pairing state in SRO and the mixing of different superconducting order parameters, which have not previously been possible with single crystal samples.

To bridge these novel superconducting states at oxide interfaces, further materials developments are critical. The global interest in unconventional superconductivity and recent high-impact realisations could lead to transformative science and simultaneously offer new paradigms of cryogenic computing and encryption.

To lead this research, the Cambridge and Kyoto hubs will bring together different specialities including superconductivity, thin-film and crystal growth of oxides, materials characterization (XMCD, low energy muon spectroscopy, pump-probe terahertz spectroscopy, angle-resolved photoemission, electron microscopy), nanofabrication and theory. The members of the Network will work closely together with PhD students, PDRAs and investigators undertaking routine research visits between the member groups. As importantly the Network will actively engage with the wider scientific community through the organisation of conferences and student workshops, and research visits with the overarching aim of triggering a long-term global effort to lift basic science to application.

Planned Impact

The premise of our International Network is to radically advance the experimental and theoretical science of unconventional superconductivity at oxide interfaces. By establishing the core teams in Cambridge and Kyoto Universities as research flagships and hubs in the area of unconventional superconductivity and oxide interfaces, we will use our Network to inspire a global research effort in this field with the broad aim of underpinning the application of new superconducting/quantum phenomena. By exploring new methods to control the pairing state of the unconventional superconductors we hope to greatly enhance the understanding of novel mechanisms of superconductivity. The aims and objectives set out in detail the expected outcomes of this research. Although in the short-term these advances will mainly impact on the academic community, there are identified long-term application areas for this research. For example, the European roadmap on superconductive electronics highlights the importance of unconventional devices for controlling the phase shift in digital circuits and requirement for much lower power computing for data centres. In the latter case, superconducting spintronics could help to minimise significantly this power consumption problem by offering energy efficient spintronic circuits in which complex circuit operation will be possible with minimal ohmic heating. For integrated circuits, particularly those operating within large-scale installations such as data centres, these power gains would greatly exceed the additional cooling overhead required to reach the superconducting state. In the USA, IARPA has recently launched a cryogenic computing initiative targeting exactly this issue.

From a basis anchored in fundamental theory and basic experiments, the principles, methodology and programmatic output of the Network can therefore realistically inform and direct the technical development of a new generation of superconducting and quantum technologies. Aspects of this research also have the potential to impact on the distant prospect of quantum computing via devices based on Majorana fermions.

Strategic roadsmapping and horizon scanning will extend well beyond the duration of this grant. Emerging and maturing superconducting and quantum technologies will in the longer term affect many industries, including electronics, communications, sensing and security. Through the Cambridge and Kyoto hubs, our capability and expertise will be continuously promoted including to companies identified as longer-term beneficiaries. Spin-out formation and licensing of IP for commercial uptake of our findings will lead to direct economic impact in the UK and Japan, as the academic research base strength will attract industrial R&D presence around it. Early-career researcher training through the Network will become a source of highly skilled workforce for companies developing superconducting and quantum technologies en-route to market, filling the rising need for interdisciplinary and specialised graduates and ensuring first-hand transfer of knowledge and know-how. Through public outreach our cutting-edge research and capability will enthuse future generations of scientists and technologists and feed into positive perception of quantum technologies (hence the National QT Programme) in the general public.

Publications

10 25 50
 
Description P-wave superconductivity in SRO is extremely sensitive to disorder and so even in epitaxial SRO thin-films sufficient point defects and strain due to lattice mismatch prevent full superconducting transition. The UK team have recently deposited epitaxial SRO on strontium titanate with incipient superconductivity, but to obtain better results a significant reduction in point defects and strain are required. We will explore growing SRO thin-films by pulse laser deposition on perfectly lattice-matched (zero strain) substrates of non-superconducting materials. This objective has recently been achieved, and the results are currently being written up for publication in Nature. This work paves the way to making p-wave devices. Another key aspect of the programme is to facilitate great international collaboration in the field of oxide superconductivity. To do this, the programme has successful organised workshops in Japan, South Korea, Italy as a workshop is scheduled in Germany in October 2020.
Exploitation Route The creation of thin-films of superconducting SRO214 will lead on to the development of p-wave superconducting devices which is exciting not only the field of superconductivity but also the field of quantum physics.
Sectors Digital/Communication/Information Technologies (including Software)

 
Description Leverhulme Visiting Professorship
Amount £91,620 (GBP)
Funding ID VP1-2016-043 
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 12/2017 
End 12/2018
 
Description Standard Research - NR1
Amount £684,502 (GBP)
Funding ID EP/P026311/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 04/2017 
End 03/2022
 
Title Magnetic Exchange Fields and Domain Wall Superconductivity at an All-Oxide Superconductor-Ferromagnet Insulator Interface 
Description research paper 
Type Of Material Database/Collection of data 
Provided To Others? Yes  
 
Title Research data supporting: Structural properties of thin-film ferromagnetic topological insulators 
Description Origin windows of all figures in the article 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Impact
URL https://www.repository.cam.ac.uk/handle/1810/267919
 
Title Research data: Magnetic exchange fields and domain wall superconductivity at an all-oxide superconductor / ferromagnetic insulator interface 
Description Origin windows of all figures in the article 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Title Research data: Magnetic exchange fields and domain wall superconductivity at an all-oxide superconductor / ferromagnetic insulator interface 
Description Origin windows of all figures in the article 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Title Research data: Magnetization-control and transfer of spin-polarized Cooper pairs into a half-metal manganite 
Description Origin windows of all figures in the article 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
 
Title Research data: Magnetization-control and transfer of spin-polarized Cooper pairs into a half-metal manganite 
Description Origin windows of all figures in the article 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
 
Description EPSRC-JSPS 
Organisation Seoul National University
Country Korea, Republic of 
Sector Academic/University 
PI Contribution We provide device characterisation expertise.
Collaborator Contribution Prof. Noh is an Expert in optical studies of transition-metal oxides and in layer-by-layer growth by molecular beam epitaxy of thin-films and pulse laser deposition, as well as advanced materials characterisation techniques, including: XMCD, pump-probe terahertz spectroscopy, and angle-resolved photoemission. His group are providing thin films to Cambridge and training students in my group including secondments.
Impact https://www.oxidesuperspin.org
Start Year 2017
 
Description EPSRC-JSPS 
Organisation University of Kyoto
Department Department of Physics
Country Japan 
Sector Academic/University 
PI Contribution The project with the EPSRC is in collaboration with the JSPS in Japan. We provide thin film growth expertise and materials of metallic and oxide based materials.
Collaborator Contribution Professor Yoshi Maeno provides state of the art growth and measurement facilities of single crystals of superconducting and magnetic materials.
Impact We organised a workshop Kyoto in November 2017 in order to bring together world leading experts in unconventional superconductivity. Over 80 people attended the meeting with 21 invited lectures. Prior to the workshop we organised two-days of tutorials for undergraduate and graduate students with topics including the theory of superconductivity and magnetism, device fabrication and characterisation. More details here: http://www.oxidesuperspin.jp/oss2017/index.html
Start Year 2017
 
Description Kavli Royal Society workshop on "Non-equilibrium superconductivity and spintronics" 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Theo Murphy international scientific meeting organised by Professor Mark Blamire, Dr Chiara Ciccarelli, Professor Matthias Eschrig, Dr Jason Robinson and Professor Lesley Cohen. This meeting brought together leading researchers in the fields of magnetism and superconductivity to explore new functionality in which spin, charge and superconducting phase coherence can work together. Their discoveries and predictions form the foundation for the field of superconducting spintronics which could eventually be developed as a replacement for large-scale semiconductor-based logic and memory.
Year(s) Of Engagement Activity 2019
URL https://royalsociety.org/science-events-and-lectures/2019/02/superconductivity-spintronics/
 
Description OSS2017 Workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact This was a student workshop including tutorials and lectures by world-leading experts in magnetism and superconductivity (21 speakers). The aim was to attract greater interest from young physics students in superconductivity. 70% of the audience were under 24 year olds undertaking their first degree.
Year(s) Of Engagement Activity 2017
URL http://www.oxidesuperspin.jp/oss2017/index.html
 
Description Oxide Superspin (OSS) Workshop Italy 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact OSS2018 was organized within the Core-to-Core Oxide SuperSpin International Network involving experimental and theoretical groups in UK, Japan, South Korea, and Italy. The aim of OSS2018 is to bring together members of the Network along with leading scientists in the field of advanced materials and interface research to discuss frontier research in the area of novel superconductivity at oxide superconductor interfaces with magnetic materials.

Through a better understanding of materials processing and properties, one can envision achieving full control over superconducting symmetry at oxide interfaces and to be able to gain access to the fundamental mechanisms underlying the science of advanced oxide interfaces and unconventional superconductivity.
The workshop will cover both theoretical and experimental aspects of the field, with a focus on structural, magnetic and electronic properties of superconducting heterostructures, correlated electron matter, topological insulators and semimetals, surface states of topological systems and their interplay with conventional orders.
Year(s) Of Engagement Activity 2018
URL http://oss2018.physics.unisa.it/aim.html
 
Description Oxide Superspin Summer Colloquium 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact 80 scientists including undergraduates, post-graduates, tenured academics and industry attended the meeting which focused on superconductivity at oxide interfaces.
Year(s) Of Engagement Activity 2018
URL https://www.oxidesuperspin.org/media/colloquium.pdf
 
Description School lecture at St Mary's Girls School Cambridge 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact I gave a morning of talks and demonstrations on magnetism and superconductivity to groups of 4-8 year old girls.
Year(s) Of Engagement Activity 2019
 
Description Superconducting Spintronics mini conference 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact International superconductivity conferences in Cambridge with 85 delates including undergraduates, post-graduates and international academics covering the UK, Israel, USA and France.
Year(s) Of Engagement Activity 2018
URL https://www.superspintronics.org/superspin.pdf