Emergent phenomena in novel correlated materials

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


An important phenomenon in Nature is that of organization of many objects interacting together, which results into new entities with properties that are much more than the sum of the parts . For example the ability to think is a property of the brain as a whole and is the result of interactions that involves numerous neurons exchanging information in an organized way and is not a property of a single individual neuron. Similarly, in many technologically-important materials electrons also show a certain degree of order in that they correlate their motion with one another to avoid the strong repulsion that arise when they are brought close together. Such correlation effects can lead to surprising emergent material properties, which often can not be predicted in advance, such as superconductivity, where current flows with no resistance due to the fact that electrons travel in pairs in a very robust way. This proposal is to explore superconductivity and other novel form of electronic order stabilized by strong correlations in complex materials that are often not found in Nature but are artificially synthesized with the purpose to achieve certain material functionality. In 2008 the discovery of superconductivity a large class of materials based on Iron stimulated a revolution in condensed matter physics. This was most unexpected as usually Iron has strong ferromagnetic properties (attracting metals) that would normally destroy a superconducting state by breaking the special pairing between electrons. The large number of structural combinations in which iron-based superconductivity is found has raised the hope that the periodic table still holds the key to the discovery of new materials with extremely high superconducting temperatures which one day will revolutionize our way of living. In my first project I propose to take on the challenge of exploring deep into the nature of structural configurations, predicting electronic behaviors and testing experimentally novel superconductors. My second project aims to explore how electrons organize themselves in the presence of frustrated magnetic interactions. Imagine a restaurant with a number of triangular tables and a large number of male and female guests; if one tries to arrange guests such that everybody sits next to a person of the opposite sex, it cannot be realized even for one single table and many equally-unsatisfactory arrangements exist. The same kind of decision has to be made by magnetic spins which can point up or down on a triangular lattice and they cannot decide, so become frustrated. How electrons organize themselves and how they travel in such circumstances remains a mystery. Another amazing unexplored behaviour is that in which electrons are able to flow freely on the surface of a material but not inside it, giving rise to an insulator with a surface that conducts electricity. In this kind of topological insulator, as also in certain frustrated systems, conventional laws of physics do not apply as particles could be found in a superposition of several states at the same time, property that could be important for use in future quantum computers.For this research I use and plan to develop the most advanced tools for probing electron correlations in micron-size single crystalline materials using the highest magnetic fields in the world (a million times larger than earth's magnetic field), low temperatures near absolute zero and extreme high pressures to tune interactions and probe new electronic phases of matter.

Planned Impact

While future scientific endeavor is difficult to predict in advance, the discovery of unexpected physics displayed by strongly correlated systems with markedly improved multifunctional properties compared with widely used semiconductors will one day have a dramatic effect on our lives. Emergent phenomena, in which the correlated behavior of many particles leads to collective new properties, are of great significance across a broad range of areas in science. However, the objective is to tailor a material (starting with its chemical composition, constituent phases) in order to obtain a desired set of properties suitable for a given application. Today technological advances are based on semiconductor physics due to their high degree of precise processing. However, if the same can be achieved for strongly correlated materials which have multifunctional and unique properties, such as superconductivity and magnetism. not found in semiconductors, would open up remarkable technological possibilities. Superconductivity is one of the most exciting phenomenon and has the potential to change significantly our life with applications in energy storage and transport (reducing dramatically the energy cost as the current flows without resistance), in medical investigations (as the case of MRI machines) or high speed trains (like the bullet train in Japan). To answer the feasibility of room temperature superconductivity requires that we solve the mechanism of high temperature superconductivity and this research will aims to contribute significantly towards that effort. Discovery of a new phase of matter is an excitement that any scientist is drawn into exploration. As understading the nature of simple metals has helped to manipulate and process semiconductors in a very precise way, the predicted novel states of matter in geometrically frustarted systems with mobile electrons or the newly discovered toplogical insulators provide avenues for the manipulationg and realization of fault-tolerant quantum computing which one day will increase the ability to simulate and predict the behaviour of systems made of infinite number of contituents. The results of this research will made available to other scientists and to the wider public though websites, newsletters and science reports aimed at a cross-disciplinary audience and also significant effort will be made to ensure that the excitment and the wonder of scientific exploration is passed on to future generations of scientists through training of students and also engagement with schools.


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Description Our research explores the unexpected emergent phenomena present in novel quantum materials mediated by strong electronic correlations. We have explored the fundamental electronic behaviour of newly discovered quantum materials using state-of-the art experimental techniques, including ultra-high magnetic fields, synchrotron facilites and first-principle band structure calculations. We have created precise quantum maps of the electronic structure of different iron-based superconductors that have formed that the basis of different theoretical models to describe and predict how superconductivity can be enhanced. Using extreme conditions of high magnetic fields and applied pressure, we have identified how electrons interact with each other and how different types of superconducting pairing compete with each other to enhance superconductivity. We have identified a new iron-based superconductor with large critical transition temperature and upper critical field as a candidate for high-magnetic field technologies. We have established the key ingredients of the nematic electronic states of iron-chalcogenide superconductors. We have developed and investigated thin flakes of superconductors.
Exploitation Route Our quantum maps of the electronic structure of different iron-based superconductors have formed that the basis of different theoretical models to describe and predict how superconductivity can be enhanced. The tuning of superconductivity under extreme conditions will help to identify the essential pairing mechanism to stabilize high-temperature superconductivity. The quantum devices based on thin flake superconductors are the first step towards tunable superconducting applications.
Sectors Education,Energy,Manufacturing, including Industrial Biotechology,Other

URL https://www2.physics.ox.ac.uk/contacts/people/coldeaa
Description The work on novel superconductors has opened the possibility to create a direct link with local industries working on superconducting applications, as a part of the Oxford Centre for Applied Superconductivity. Our group has tested a versatile probe developed by Oxford Instruments using quantum materials developed during the research grant. We have identified a new iron-based superconductor with large critical transition temperature and upper critical field as a candidate for high-magnetic field technologies and pursue the development of superconducting wires. The students and staff related to this award have developed extensive expertise in developing new experimental projects and computational tools, analysing and presenting complex information and data towards their new jobs either in research, software companies and financial sector. The development of thin flake devices has lead to the research development of superconducting thin flake devices.
First Year Of Impact 2015
Sector Energy,Manufacturing, including Industrial Biotechology
Impact Types Societal,Economic

Description Oxford Centre for Applied Superconductivity
Amount £1,550,000 (GBP)
Funding ID http://www.cfas.ox.ac.uk/ 
Organisation Local Enterprise Partnerships 
Sector Charity/Non Profit
Country United Kingdom
Start 04/2015 
End 12/2022
Description Oxford Quantum Materials Platform Grant
Amount £1,736,109 (GBP)
Funding ID EP/M020517/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 04/2015 
End 03/2020
Description ARPES 
Organisation Diamond Light Source
Country United Kingdom 
Sector Private 
PI Contribution Performing, analyzing and publishing work together. We provided samples and developed our own software to analyze ARPES data on Fe based superconductors.
Collaborator Contribution Provide technical help and complementary analysis tools.
Impact Beamtime awarded on the Diamond I05 beamline. Training of a PhD student which now is employed by the Diamond Light Source Title: Emergence of the nematic electronic state in FeSe Author(s): Watson, M. D.; Kim, T. K.; Haghighirad, A. A.; et al. Source: Physical Review B Volume: 91 Issue: 15 Published: 2015 DOI: 10.1103/PhysRevB.91.155106 Title: Suppression of orbital ordering by chemical pressure in FeSe1-xSx Author(s): Watson, M. D.; Kim, T. K.; Haghighirad, A. A.; et al. Source: Physical Review B Volume: 92 Issue: 12 Published: 2015 DOI: 10.1103/PhysRevB.92.121108
Start Year 2014
Description DFT collaboration 
Organisation Goethe University Frankfurt
Country Germany 
Sector Academic/University 
PI Contribution DFT and DMFT calculations
Collaborator Contribution Experimental and computational studies to understand the electronic structure and electronic correlations of FeSe measured using angle-resolved photoemission spectroscopy.
Impact Formation of Hubbard-like bands as a fingerprint of strong electron-electron interactions in FeSe Matthew D. Watson, Steffen Backes, Amir A. Haghighirad, Moritz Hoesch, Timur K. Kim, Amalia I. Coldea, and Roser Valentí Phys. Rev. B 95, 081106(R) - Published 22 February 2017
Start Year 2011
Description Institute of High Pressure Physics 
Organisation Polish Academy of Sciences
Department Institute of High Pressure Physics
Country Poland 
Sector Public 
PI Contribution Development of superconducting wires based on fundamental research on new candidate superconductors.
Collaborator Contribution Institute of High Pressure Physics (IHPP), also known as "Unipress", was founded in 1972 by Polish Academy of Science and contributes to the development of superconducting wires.
Impact Development of superconducting wires for magnet development technology.
Start Year 2018
Description Oxford Quantum Materials 
Organisation University of Oxford
Department Quantum Materials
Country United Kingdom 
Sector Academic/University 
PI Contribution Oxford Quantum Materials Platform Grant
Collaborator Contribution Oxford Quantum Materials Platform Grant
Impact Oxford Quantum Materials Platform Grant (1,736,109) Physics, Materials, Chemistry Recent relevant publication: Ideal Weyl semimetal induced by magnetic exchange J.-R. Soh, F. de Juan, M. G. Vergniory, N. B. M. Schröter, M. C. Rahn, D. Y. Yan, J. Jiang, M. Bristow, P. Reiss, J. N. Blandy, Y. F. Guo, Y. G. Shi, T. K. Kim, A. McCollam, S. H. Simon, Y. Chen, A. I. Coldea, and A. T. Boothroyd Phys. Rev. B 100, 201102(R) - Published 13 November 2019
Start Year 2013
Description OUTREACH Schools 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Talks and demonstrations to primary school children

The children got excited about the science presented. Parents confirmed the children interest in the presented talk and demonstrations.
Year(s) Of Engagement Activity 2011,2012,2013,2014
Description Open days 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Laboratory visits from public and prospective students to present active research;
Year(s) Of Engagement Activity 2014
Description Oxford Symposium on Quantum Materials 
Form Of Engagement Activity Scientific meeting (conference/symposium etc.)
Part Of Official Scheme? Yes
Type Of Presentation workshop facilitator
Geographic Reach Regional
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Research activities were presented. Collaborations were formed. New experiments performed.

This is an annual interdisciplinary forum to bring together physicists, chemists, materials scientists and theoreticians in and around Oxford to advance the science and promote direct collaboration between groups interested in novel quantum materials and phenomena. This is an annual forum which has generated discussions with scientists and industry and collaborations.
Year(s) Of Engagement Activity 2011,2012,2013,2014
URL https://www2.physics.ox.ac.uk/research/quantum-materials/group-activities/oxford-symposium-on-quantu...
Description Superconductivity -laboratory visits 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Annual involvement in laboratory tours to explain to the public the scientific significance and the practical applications of superconductivity.
Year(s) Of Engagement Activity 2017,2018,2019
URL https://www2.physics.ox.ac.uk/about-us/outreach