New approaches to iron-based superconductors

Lead Research Organisation: University of Oxford
Department Name: Oxford Chemistry

Abstract

In 2008 a new series of high temperature superconductors containing iron arsenide, phosphide or selenide layers was discovered and in the last 2 years major research efforts have attempted to understand the phenomenon. New superconductors generate enormous interest as they are important in the manufacture of superconducting magnets for high field applications and in the manufacture of superior components for certain telecommunications and electronic devices. The discovery of new superconductors, particularly those which exhibit unconventional behaviour and do not conform to the Bardeen-Cooper-Schrieffer model, offers the possibility of superconductivity at temperatures approaching ambient and is an example of blue-skies research which may have an important technological payoff in the future. The research in this area has shown that several compounds with similar structural features exhibit superconductivity, but the fundamental measurements have probed a rather small number of these compounds - those which are most amenable to crystal growth. While most groups have been focused on existing compounds, the most direct route to substantial progress in this area is via innovative materials discovery and our unique strategy includes an attempt to synthesise new classes of compound with iron arsenide or iron selenide layers which may have superior properties to the materials discovered thus far. In particular our focus is on using low temperature synthesis to access compositions which are not thermodynamically stable at high temperatures. This is expected to open a new chapter in the study of these superconductors. The synthesis will be carried out in parallel with physical property measurements in the laboratory and at international facilities which will be important for understanding how the superconductivity and magnetism in these compounds is correlated with composition and crystal structure. These results will be fed back into the synthetic programme. Samples of the new compounds will be made available to other members of the community whose expertise is in specialised measurements of physical properties. Ultimately the research may yield new superconducting materials, correlations between composition, crystal structure and physical properties in these materials, and also offer fundamental insights into why these materials superconduct, possibly paving the way for predictive theoretical treatments of the phenomenon of unconventional superconductivity .

Planned Impact

We propose fundamental research in a rapidly developing area at the interface of solid state chemistry and condensed matter physics. The main outputs from this research will be: (1). new superconducting materials and investigations of their properties which will be disseminated in high-profile journals and at conferences; and (2). trained researchers who have worked in a competitive and fast-moving area of science. The immediate beneficiaries of these outputs (i.e. on the timescale of the grant) will be: (1). Other academics who will use our discoveries to understand the phenomenon of unconventional superconductivity. (2). The UK scientific community (academic and industrial) who will gain experienced researchers and high-profile research outputs. Superconductors are important in a wide range of technological applications ranging from medical imaging to telecommunications and energy efficiency. The transition temperature is by far from being the only parameter relevant for applications and the full characterization of new materials can often yield particular special properties that makes a new superconductor ideal for a particular niche application. If the new superconductors discovered during this research have properties which make them attractive in certain applications then there may be very substantial and transformative benefits to UK industries and society as a whole. These impacts are much less easy to predict and will be realised on the timescale of a few years to decades.

Publications

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Taylor AE (2013) Absence of strong magnetic fluctuations in FeP-based systems LaFePO and Sr2ScO3FeP. in Journal of physics. Condensed matter : an Institute of Physics journal

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Cassidy SJ (2018) Complex Magnetic Ordering in the Oxide Selenide Sr2Fe3Se2O3. in Inorganic chemistry

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Cassidy SJ (2016) Complex Microstructure and Magnetism in Polymorphic CaFeSeO. in Inorganic chemistry

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Cassidy S (2014) Local Structure of Sodium- and Iron-deintercalated NaFeAs in Zeitschrift für anorganische und allgemeine Chemie

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Corkett AJ (2015) Spin-reorientation transition in CeMnAsO. in Inorganic chemistry

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Free D (2012) Sr 2 Mn 2 O 4 Se: A New Oxychalcogenide with Antiferromagnetic Chains in Zeitschrift für anorganische und allgemeine Chemie

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Ghannadzadeh S (2014) Upper critical field of NaFe 1 - x Co x As superconductors in Physical Review B

 
Description We have discovered the factors that control high temperature superconductivity in iron-based superconductors through a series of high quality and definitive experiments on a wide range of compounds, several of which have been adopted more widely by the international community
Exploitation Route The results will be used for further experiments and for developing theories.
Sectors Chemicals,Education,Energy

URL http://research.chem.ox.ac.uk/simon-clarke.aspx
 
Description Leverhulme Research Project Grant
Amount £143,884 (GBP)
Funding ID RPG-2014-221 
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 12/2014 
End 11/2017
 
Description Studentship
Amount £35,000 (GBP)
Organisation Diamond Light Source 
Sector Private
Country United Kingdom
Start 09/2014 
End 09/2017
 
Description EMAT 
Organisation University of Antwerp
Department Electron Microscopy for Materials Science (EMAT)
Country Belgium 
Sector Academic/University 
PI Contribution My research team provided samples of electronically unusual materials for electron microscopy.
Collaborator Contribution The Antwerp team provided electron microscopy expertise that is probably unparalleled in the world. This has enabled definitive publications of new results
Impact Several publications in high impact journals. New data to inform further chemical synthesis. This is a single discipline collaboration