Superconducting Spintronics

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

Abstract

This programme will study the synergy between superconductivity and magnetism which can be engineered in certain devices and use this to demonstrate superconducting spintronics as future computing technology.

In ferromagnetic metals, an internal exchange field generates an imbalance in the number of electrons with up and down spins which means that currents that emerge from ferromagnets into non-magnetic metals carry a net spin in addition to charge. Such spin polarized currents are utilized for logic and sensor applications (for example in hard disk drives), and finding ways to generate and control them is a major goal of spin electronics (spintronics). However, the heat loss from the charge currents used to generate spin currents can be considerable and this is one reason why applications of spintronics, such as integrated memory chips, are presently limited.

In superconductors charge can flow without dissipation but, since the Cooper pairs consist of electrons with antiparallel spins, charge currents cannot carry spin. Further, since Cooper pairs are easily disrupted by magnetism, the coupling of superconductivity and ferromagnetism might appear useless for applications in spintronics. However, during the past few years a series of discoveries have shown that, not only can magnetism and superconductivity be made to cooperate, but in carefully engineered superconductor/magnet systems new functionality can be created in which spin, charge and superconducting phase coherence can work together. By combining these different degrees of freedom a whole new spectrum of recent predictions is waiting to be explored experimentally.
Through this ambitious programme we have the chance to transform this array of predictions and discoveries about the interaction between superconductivity and magnetism into a demonstration technology which could eventually be developed as a replacement for large-scale semiconductor-based logic. Our ideas for the proposed field of superconducting spintronics go far beyond the simple ideas of eliminating resistive losses inherent in conventional spin electronic (spintronic) circuits, but instead aim to exploit unique attributes of the superconducting state to control spin currents and spin accumulation.

The programme brings together teams from three different specialties - superconducting devices, high speed spintronics and theory of strong correlations in mesoscopic physics - which will work together to identify and investigate the key underpinning science. This basic science which will emerge from the programme will allow us to understand which of the many predicted effects are viable for long-term development.

The flexibility of a Programme Grant will allow us to work in parallel on all the potential elements and then progressively focus on those that show most promise for demonstrator devices: firstly a memory device which can store data indefinitely but can be switched with ultra-low energy and, secondly, some form of logic device. The latter may be a transistor-like structure or one of the all-spin logic devices proposed for conventional spintronics. The ambition for these superconducting spintronic devices is that they will combine the scalability inherent in conventional spintronics and the high speed and low power offered by superconductors. The risks are such that we may not be able to realise all of these ideas but, by working in parallel on a wide range of different phenomena which couple superconductivity and spin transport, we have a unique opportunity to define a new technology field.

Planned Impact

The programme will focus on fundamental research which combines unconventional superconductivity and magnetism. The primary impact of the research will be greatly improved understanding of the behaviour of spin within hybrid magnetic / superconducting systems. Although this is itself a very active field within the UK and internationally, many aspects of these results are expected to extend beyond the immediate subject area to include fields such as quantum technology, unconventional superconductivity, and more general exotic states in condensed matter systems. In the longer term, we expect that the outputs of our research will form the foundation for a new technology - superconducting spintronics - for memory and logic devices that can operate with minimal Joule heating. While in present devices logic information is encoded using transistors as control switches between two different states, in the new devices information will be encoded via electron spin orientation, using input and output elements that are totally different from field-effect transistors. The resulting redesign will open up new avenues for investigation through evolutionary change and discontinuous revolutionary hardware architecture.

Publications

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Ahmed I (2018) Radio-Frequency Capacitive Gate-Based Sensing in Physical Review Applied

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Balkind E (2019) Magnetic skyrmion lattice by the Fourier transform method in Physical Review B

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Di Bernardo A (2019) Nodal superconducting exchange coupling in Nature Materials

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Feng Z (2017) Out of plane superconducting Nb/Cu/Ni/Cu/Co triplet spin-valves in Applied Physics Letters

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Gomez-Perez J (2018) Synthetic Antiferromagnetic Coupling Between Ultrathin Insulating Garnets in Physical Review Applied

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Gomez-Perez J (2018) Synthetic Antiferromagnetic Coupling Between Ultrathin Insulating Garnets in Physical Review Applied

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Rogdakis K (2018) Electric power transfer in spin-pumping experiments in Applied Physics Express

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Yates KA (2018) Andreev reflection spectroscopy in transition metal oxides. in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

 
Description We have discovered experimentally that, under certain circumstances, spin currents may flow more effectively through a conventional s-wave superconductor than in the normal state. This provides the basis for the transmission of electron spin information within a superconducting circuit. This work has now been extended in which we are are to control the pure spin current density via Rashba epin orbit coupling. This is central to control of spin in the superconducting state and offers the potential for electronic control of superconducting spins.
Exploitation Route Other workers in the field of superconductivity and those engaged in Advanced Materials Research, particularly in the area of spintronics and ICT.
Sectors Digital/Communication/Information Technologies (including Software)

 
Description Government Office for Science project: 'Future Demand for Materials'
Geographic Reach National 
Policy Influence Type Gave evidence to a government review
 
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 Exchange paper data 
Description Data to support superconducting exchange coupling paper 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Impact Published Nature Materials paper 
URL https://doi.org/10.17863/CAM.1286
 
Title FMR triplet spin current data 
Description Data underlying Nature Materials submission 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? No  
Impact Provisionally accepted Nature Materials paper 
URL https://doi.org/10.17863/CAM.20719
 
Title Feng spin valve data 
Description Data in support of triplet spin valve paper 
Type Of Material Data analysis technique 
Year Produced 2017 
Provided To Others? Yes  
Impact Data supporting APL paper 
URL https://doi.org/10.17863/cam.11539
 
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 Out of plane superconducting Nb/Cu/Ni/Cu/Co triplet spin-valves 
Description © 2017 Author(s). The critical temperature of a triplet superconducting spin valve depends on the effectiveness of the conversion of singlet pairs in the superconductor into triplet pairs which can penetrate a ferromagnet and so drive a strong proximity effect. Here, we compare the out-of plane field dependence of the critical temperature in transition metal triplet spin valves with otherwise equivalent samples in which the singlet-triplet converting spin mixer ferromagnet layer is omitted. We report a significant field-dependent difference between the samples, which is consistent with a magnetisation orientation dependent spin mixing efficiency in the spin valve. 
Type Of Material Database/Collection of data 
Year Produced 2017 
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: 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  
 
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 Superconducting Pure Spin Currents 
Description Broadband FMR spectroscopy 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Description GdN measurements in Naples 
Organisation University of Naples
Country Italy 
Sector Academic/University 
PI Contribution Provided samples and ideas on transport properties
Collaborator Contribution Detailed low temperature measurements and theoretical modelling
Impact 1. D. Massarotti, et al., Physica C: Superconductivity and its Applications 533 53 (2017). 2. D. Massarotti, et al., Phys. Rev. B 98 144516 (2018). 3. R. Caruso, et al., Phys. Rev. Lett. 122 047002 (2019).
Start Year 2016
 
Description Lateral devices with Kyushu 
Organisation Kyushu University
Country Japan 
Sector Academic/University 
PI Contribution Introduced the ideas and techniques for spin triplet pairing
Collaborator Contribution Optimised deposition equipment in Cambridge for evaporation of lateral devices and prepared devices in Japan for measurement in Cambridge.
Impact None yet
Start Year 2018
 
Description Cambridge Research Horizons Article of Superconducting Spintronics 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact "The electron manifesto" article was an invited contribution written to publicise our basic research programme.
Year(s) Of Engagement Activity 2017
URL http://www.cam.ac.uk/system/files/issue_33_research_horizons.pdf
 
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 Royal Society Meeting 
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 Kavli meeting at Chicheley Hall - aim was to bring together superconducting and conventional spintronics communities
Year(s) Of Engagement Activity 2019
URL https://royalsociety.org/science-events-and-lectures/2019/02/superconductivity-spintronics/
 
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