Topological effects in high magnetic fields
Lead Research Organisation:
University of Oxford
Department Name: Oxford Physics
Abstract
This proposal aims to explore the fundamental properties of new candidate systems of topological insulators in highly crystalline materials by using high magnetic fields, applied strain and low temperatures where quantum effects can be tested. Topological insulators are a new phase of matter. Due to the strong spin-orbit interaction, these electronic systems have insulating bulk properties while maintain topologically protected metallic surfaces on their surfaces or edges. In ordinary materials, backscattering, in which electrons take a turn back owing to collisions with crystal defects, thus reducing the current flow and increasing its resistance. On the surface of topological insulators, backscattering processes are completely suppressed, so charge transport is in a low-dissipation state with exceptional transport mobility and reduced energy consumption, which is extremely attractive for semiconductor devices. As a result of unintended doping from crystal imperfections, however, residual bulk carriers are always present in the actual samples and often dominate the total conductivity. Low-dimensional nanostructures, with a large surface-to-volume ratio, provide attractive systems for transport studies, because the contribution from surface carriers is much greater than that from bulk crystals, and are therefore most relevant to electronic device applications. This research will explore the fundamental characteristics of the electronic and magnetic properties both in bulk and thin film form using nanoscale tools. This funding will develop additional expertise in designing nanoscale devices to enrich the current work in quantum materials and make significant steps towards material design and control.
Planned Impact
The proposed research is in the emerging area of topological insulators that are potential candidates for future electronic devices due to their low dissipative charge transport and full spin polarisation that are likely to be realized at room temperature. These new materials, like graphene, are likely to revolutionize the miniaturization of conventional electronics and furthermore pave the way towards significant applications in spintronics and quantum computation. The findings of our research will have significant impact, in particular the academic community who actively try to understand the behaviour of topological insulators, and electronics industry that is in search of a replacement for the conventional CMOS approach. Not only would topological insulators solve the heat dissipation problem that will become critical following further the predicted device scaling, radically new device concepts might also be feasible that involve spin-polarized currents and even quantum computation.
Training highly qualified personnel for academia and industry is a direct impact of our research. Students and PDRAs learn to use all our existing experimental techniques in magnetic fields, to develop new experiments and software, become proficient in first principle calculations and structural analysis, device nanofabrication as well as learn to become good science communicator and participate in outreach events in the department and local schools. Outreach activities will be promoted via the website though videos and developing new hands-on experiments to be used in local schools.
While there has been significant research effort, in particular abroad, new materials with even better properties have been proposed in order to reduce the impurity levels and to control the surface states. The aim of this proposal is therefore to make step-changing improvements in the fundamental understanding of the topological insulator by using available low temperature and high magnetic field techniques and combining this with material synthesis controlled at atomic scale.
Direct contact with industry will be promoted via the Impact Advisory group of Quantum Materials that has representative from Oxford Instruments, Cryogenics, Samsung though a series of poster presentations, talks, visits to their facilities. INSPIRE platform will provide also mentoring and promote links with relevant industry to the project.
Training highly qualified personnel for academia and industry is a direct impact of our research. Students and PDRAs learn to use all our existing experimental techniques in magnetic fields, to develop new experiments and software, become proficient in first principle calculations and structural analysis, device nanofabrication as well as learn to become good science communicator and participate in outreach events in the department and local schools. Outreach activities will be promoted via the website though videos and developing new hands-on experiments to be used in local schools.
While there has been significant research effort, in particular abroad, new materials with even better properties have been proposed in order to reduce the impurity levels and to control the surface states. The aim of this proposal is therefore to make step-changing improvements in the fundamental understanding of the topological insulator by using available low temperature and high magnetic field techniques and combining this with material synthesis controlled at atomic scale.
Direct contact with industry will be promoted via the Impact Advisory group of Quantum Materials that has representative from Oxford Instruments, Cryogenics, Samsung though a series of poster presentations, talks, visits to their facilities. INSPIRE platform will provide also mentoring and promote links with relevant industry to the project.
Organisations
- University of Oxford (Lead Research Organisation)
- UNIVERSITY OF OXFORD (Collaboration)
- UNIVERSITY OF GLASGOW (Collaboration)
- Heriot-Watt University (Collaboration)
- UNIVERSITY OF LEEDS (Collaboration)
- University of California, Los Angeles (UCLA) (Collaboration)
- UNIVERSITY OF LIVERPOOL (Collaboration)
- DIAMOND LIGHT SOURCE (Collaboration)
People |
ORCID iD |
Amalia Coldea (Principal Investigator) |
Publications
Alexander-Webber JA
(2018)
Multi-band magnetotransport in exfoliated thin films of Cu x Bi2Se3.
in Journal of physics. Condensed matter : an Institute of Physics journal
Blake S
(2016)
de Haas-van Alphen study of role of 4 f electrons in antiferromagnetic CeZn 11 as compared to its nonmagnetic analog LaZn 11
in Physical Review B
Blake S
(2015)
Fermi surface of IrTe 2 in the valence-bond state as determined by quantum oscillations
in Physical Review B
Bristow M
(2020)
Anomalous high-magnetic field electronic state of the nematic superconductors FeSe 1 - x S x
in Physical Review Research
Coldea A
(2019)
Evolution of the low-temperature Fermi surface of superconducting FeSe1-xSx across a nematic phase transition
in npj Quantum Materials
Collins-McIntyre L
(2014)
X-ray magnetic spectroscopy of MBE-grown Mn-doped Bi2Se3 thin films
in AIP Advances
Kwan Y
(2020)
Quantum oscillations probe the Fermi surface topology of the nodal-line semimetal CaAgAs
in Physical Review Research
Narayanan A
(2015)
Linear Magnetoresistance Caused by Mobility Fluctuations in n -Doped Cd 3 As 2
in Physical Review Letters
Prentice J
(2016)
Modeling the angle-dependent magnetoresistance oscillations of Fermi surfaces with hexagonal symmetry
in Physical Review B
Shen B
(2018)
Significant change in the electronic behavior associated with structural distortions in monocrystalline SrAg 4 As 2
in Physical Review B
Soh J
(2019)
Ideal Weyl semimetal induced by magnetic exchange
in Physical Review B
Watson M
(2016)
Evidence for unidirectional nematic bond ordering in FeSe
Watson M
(2015)
Emergence of the nematic electronic state in FeSe
Watson M
(2015)
Emergence of the nematic electronic state in FeSe
in Physical Review B
Watson M
(2016)
Evidence for unidirectional nematic bond ordering in FeSe
in Physical Review B
Watson M
(2015)
Suppression of orbital ordering by chemical pressure in FeSe 1 - x S x
in Physical Review B
Watson M
(2017)
Formation of Hubbard-like bands as a fingerprint of strong electron-electron interactions in FeSe
in Physical Review B
Watson M
(2013)
Study of the structural, electric and magnetic properties of Mn-doped Bi 2 Te 3 single crystals
in New Journal of Physics
Watson MD
(2015)
Dichotomy between the Hole and Electron Behavior in Multiband Superconductor FeSe Probed by Ultrahigh Magnetic Fields.
in Physical review letters
Description | Novel electronic system in which electrons travel with high mobility have an immense potential for electronic devices. In these Dirac materials the fundamental electronic dispersion are highly unusual, different from those found in normal metals, and they can be found in graphene, topological insulators or Dirac semi-metals. We have found that unusual large and linear magnetoresistance in a Dirac semimetal can be strongly affected by the presence of imperfections in crystals. We have also investigated the role of magnetic ions in topological materials, both as single crystals and thin films and found the magnetic ordering found in Mn-doped Bi2Te3 is largely independent of the chemical potential of the host material and the magnetic ions are prone to form clusters in these systems. We have made the first steps towards developing devices based on exfoliated single crystals and nanowires of Dirac materials in Cu-doped Bi2Se3. We have set up new collaborations with scientists in Oxford, USA and Poland to explore new Dirac materials and describe their electronic behaviour. We have trained post-graduate and undergraduate students to develop both experimental, computational skills to describe the electronic behaviour of novel materials with Dirac dispersions. |
Exploitation Route | This award has enabled research into new materials with unusual Dirac dispersions which have extremely high mobilities both in the bulk or on their surfaces. The linear response to magnetic fields together with their remarkable high mobilities makes them suitable future potential electronic devices and magnetic field sensors Our work have been highly cited by our peers working in related research areas leading to enhanced knowledge transfer. |
Sectors | Electronics Energy Other |
URL | https://www2.physics.ox.ac.uk/contacts/people/coldeaa |
Description | 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 linear response to magnetic fields together with their remarkable high mobilities makes some of the investigated materials suitable for applications in electronic devices and magnetic field sensors. The development of thin flake devices has lead to the research development of superconducting thin flake devices. |
First Year Of Impact | 2007 |
Sector | Education,Electronics,Other |
Impact Types | Societal Economic |
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 | 03/2015 |
End | 03/2020 |
Title | Evidence for unidirectional nematic bond ordering in FeSe |
Description | These data are related to the paper https://arxiv.org/abs/1603.04545 to be published in Physical Review B in 2016. Raw data files are in .nxs format, which are standard HDF5 format files created at I05 at diamond. PDF figures have some basic description in the filename. |
Type Of Material | Database/Collection of data |
Year Produced | 2016 |
Provided To Others? | Yes |
Impact | n/a |
Title | FeSe_magneotransport_Watson_PRL_2015 |
Description | These data constitute the data presented in the plots of Figures 1 and 2 in "Dichotomy between the Hole and Electron Behavior in the Multiband FeSe Probed by Ultrahigh Magnetic Fields" (Watson, PRL, 2015). The figures were created in Origin, but can be reproduced in any graphing software that can import standard ASCII files. The resistivity and Hall effect data has been scaled by the sample geometry into resistivty (not resistance) units. The data were collected in the Clarendon Laboratory, Oxford University and at the EMFL high magnetic field facilities in Toulouse. |
Type Of Material | Database/Collection of data |
Year Produced | 2015 |
Provided To Others? | Yes |
Impact | n/a |
Title | Magnetotransport CuxBi2Se3 |
Description | These data were created by recording the transport behaviour on thin flakes devices at low temperatures and in magnetic field. These are all DAT files easily readable. We report magnetotransport studies in thin (<100nm) exfoliated films of CuxBi2Se3 and we detect an unusual electronic transition at low temperatures. Bulk crystals show weak superconductivity with Tc~3.5K and a possible electronic phase transition around 200K. Following exfoliation, superconductivity is supressed and a strongly temperature dependent multi-band conductivity is observed for T<30K. This transition between competing conducting channels may be enhanced due to the presence of electronic ordering, and could be affected by the presence of an effective internal stress due to Cu intercalation. By fitting to the weak antilocalisation conductivity correction at low magnetic fields we confirm that the low temperature regime maintains a quantum phase coherence length Lphiv> > 100nm indicating the presence of topologically protected surface states. |
Type Of Material | Database/Collection of data |
Year Produced | 2018 |
Provided To Others? | Yes |
Impact | Publication: Multi-band magnetotransport in exfoliated thin films of CuxBi2Se3, by J A Alexander-Webber, J Huang, J Beilsten-Edmands, P Cermák, C Drašar, R J Nicholas and A I Coldea Published 16 March 2018, Journal of Physics: Condensed Matter, Volume 30, Number 15. This work has opened up the design of devices using thin flakes of single crystals to study they magnetotransport and topological signatures. |
URL | https://ora.ox.ac.uk/objects/uuid:f9dbd74f-1f42-4d45-a236-456bee6d8d1e |
Title | Quantum oscillations in the nematic superconductors FeSe1-xSx |
Description | These are the Raw data used to generate the figures related to the publication: "Evolution of the Fermi surface of the nematic superconductors FeSe1-xSx" by A. I. Coldea et al. |
Type Of Material | Database/Collection of data |
Year Produced | 2018 |
Provided To Others? | Yes |
Impact | The existence of a nematic phase transition in iron-chalcogenide superconductors poses an intriguing question about its impact on superconductivity. To understand the nature of this unique quantum phase transition, it is essential to study how the electronic structure changes across this transition at low temperatures. Here, we investigate the evolution of the Fermi surfaces and electronic interactions across the nematic phase transition of FeSe1-xSx using Shubnikov-de Haas oscillations in high magnetic fields up to 45 T in the low temperature regime down to 0.4 K. Most of the Fermi surfaces of FeSe1-xSx monotonically increase in size except for a prominent low frequency oscillation associated with a small, but highly mobile band, which disappears at the nematic phase boundary near x ~ 0.17, indicative of a topological Lifshitz transition. The quasiparticle masses are larger inside the nematic phase, indicative of a strongly correlated state, but they become suppressed outside it. The experimentally observed changes in the Fermi surface topology, together with the varying degree of electronic correlations, will change the balance of electronic interactions in the multi-band system FeSe1-xSx and promote different kz-dependent superconducting pairing channels inside and outside the nematic phase. |
URL | https://ora.ox.ac.uk/objects/uuid:dad66609-f461-4f7d-9373-190e309a2ed9 |
Title | Simulations_AMRO_hexagonal |
Description | These data were created using Matlab over the last few years. |
Type Of Material | Database/Collection of data |
Year Produced | 2016 |
Provided To Others? | Yes |
Impact | n/a |
URL | https://ora.ox.ac.uk/objects/uuid:ffe7d5fe-00da-497e-b94c-3735eb2edf7d |
Title | Suppression of orbital ordering by chemical pressure in FeSe1-xSx |
Description | This data was collected using Diamond Light Source, beamline i05. Some of the raw data is in the nxs format of the beamline. Data were analyzed using Matlab and Origin. Each folder contains the data in different figure of the paper posted on archive: http://arxiv.org/abs/1508.05016. We report a high-resolution angle-resolved photoemission spectroscopy study of the evolution of the electronic structure of FeSe1-xSx single crystals. Isovalent S substitution onto the Se site constitutes a chemical pressure which subtly modifies the electronic structure of FeSe at high temperatures and induces a suppression of the tetragonal-symmetry-breaking structural transition temperature from 87 to 58 K for x = 0.15. With increasing S substitution, we find smaller splitting between bands with dyz and dxz orbital character and weaker anisotropic distortions of the low-temperature Fermi surfaces. These effects evolve systematically as a function of both S substitution and temperature, providing strong evidence that an orbital ordering is the underlying order parameter of the structural transition in FeSe1-xSx . Finally, we detect the small inner hole pocket for x = 0.12, which is pushed below the Fermi level in the orbitally ordered low-temperature Fermi surface of FeSe. |
Type Of Material | Database/Collection of data |
Year Produced | 2015 |
Provided To Others? | Yes |
Impact | Understanding of electronic structure and superconductivity of FeSe1-xSx |
URL | https://ora.ox.ac.uk/objects/uuid:be7c2ba3-b358-4840-b77e-7a8b70d32340 |
Title | de Haas--van Alphen study of the role of 4f electrons in antiferromagnetic CeZn11 as compared to its nonmagnetic analogue LaZn11 |
Description | These are the data generated to produce the publication entitled "de Haas--van Alphen study of the role of 4f electrons in antiferromagnetic CeZn11 as compared to its nonmagnetic analogue LaZn11" by S. F. Blake, H. Hodovanets, A. McCollam, S. L. Bud'ko, P. C. Canfield, and A. I. Coldea published in Physical Review B. |
Type Of Material | Database/Collection of data |
Year Produced | 2016 |
Provided To Others? | Yes |
Impact | We present a de Haas-van Alphen study of the Fermi surface of the low temperature antiferromagnet CeZn11 and its non-magnetic analogue LaZn11, measured by torque magnetometry up to fields of 33T and at temperatures down to 320 mK. Both systems possess similar de Haas-van Alphen frequencies, with three clear sets of features - ranging from 50T to 4kT - corresponding to three bands of a complex Fermi surface, with an expected fourth band also seen weakly in CeZn11. The effective masses of the charge carriers are very light (<1 me) in LaZn11 but a factor of 2 - 4 larger in CeZn11, indicative of stronger electronic correlations. We perform detailed density functional theory (DFT) calculations for CeZn11 and find that only DFT+U calculations with U=1.5 eV, which localize the 4f states, provide a good match to the measured de Haas-van Alphen frequencies, once the presence of magnetic breakdown orbits is also considered. Our study suggests that the Fermi surface of CeZn11 is very close to that of LaZn11 being dominated by Zn 3d, as the Ce 4f states are localised and have little influence on its electronic structure, however, they are responsible for its magnetic order and contribute to enhance electronic correlations. |
URL | https://ora.ox.ac.uk/objects/uuid:e3251001-47a6-405d-9359-02bec24ba363 |
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 | INSPIRE collaboration |
Organisation | Heriot-Watt University |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | I have initiated setting up this collaboration as part of the EPSRC INSPIRE programme. This collaboration was awarded £50,457 from EPSRC (EP/K036408/1, INSPIRE Physical Sciences: A synergy for next generation materials science). I have participated in a series of working meetings in developing common program of research. I have provided crystals to be investigated by high resolution microscopy and our group have hosted a post-doc from Herriot Watt to visit our lab and perform experiments. |
Collaborator Contribution | My collaborators have contributed to the grant proposal, new avenues of research, new experiments and calculations. New results are available that will result in new publications. |
Impact | This is a multi-disciplinary collaboration composed of Dr O Cespedes (Leeds -Physics), Dr AI Coldea (Oxford-Physics), Dr G. Teobaldi (Liverpool-Chemistry), Dr J Bos (Herriot-Watt-Chemistry), Dr DA MacLaren (Glasgow-Physics) and funded by EPSRC. Our common work will generate publications in the near future. |
Start Year | 2012 |
Description | INSPIRE collaboration |
Organisation | University of Glasgow |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | I have initiated setting up this collaboration as part of the EPSRC INSPIRE programme. This collaboration was awarded £50,457 from EPSRC (EP/K036408/1, INSPIRE Physical Sciences: A synergy for next generation materials science). I have participated in a series of working meetings in developing common program of research. I have provided crystals to be investigated by high resolution microscopy and our group have hosted a post-doc from Herriot Watt to visit our lab and perform experiments. |
Collaborator Contribution | My collaborators have contributed to the grant proposal, new avenues of research, new experiments and calculations. New results are available that will result in new publications. |
Impact | This is a multi-disciplinary collaboration composed of Dr O Cespedes (Leeds -Physics), Dr AI Coldea (Oxford-Physics), Dr G. Teobaldi (Liverpool-Chemistry), Dr J Bos (Herriot-Watt-Chemistry), Dr DA MacLaren (Glasgow-Physics) and funded by EPSRC. Our common work will generate publications in the near future. |
Start Year | 2012 |
Description | INSPIRE collaboration |
Organisation | University of Leeds |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | I have initiated setting up this collaboration as part of the EPSRC INSPIRE programme. This collaboration was awarded £50,457 from EPSRC (EP/K036408/1, INSPIRE Physical Sciences: A synergy for next generation materials science). I have participated in a series of working meetings in developing common program of research. I have provided crystals to be investigated by high resolution microscopy and our group have hosted a post-doc from Herriot Watt to visit our lab and perform experiments. |
Collaborator Contribution | My collaborators have contributed to the grant proposal, new avenues of research, new experiments and calculations. New results are available that will result in new publications. |
Impact | This is a multi-disciplinary collaboration composed of Dr O Cespedes (Leeds -Physics), Dr AI Coldea (Oxford-Physics), Dr G. Teobaldi (Liverpool-Chemistry), Dr J Bos (Herriot-Watt-Chemistry), Dr DA MacLaren (Glasgow-Physics) and funded by EPSRC. Our common work will generate publications in the near future. |
Start Year | 2012 |
Description | INSPIRE collaboration |
Organisation | University of Liverpool |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | I have initiated setting up this collaboration as part of the EPSRC INSPIRE programme. This collaboration was awarded £50,457 from EPSRC (EP/K036408/1, INSPIRE Physical Sciences: A synergy for next generation materials science). I have participated in a series of working meetings in developing common program of research. I have provided crystals to be investigated by high resolution microscopy and our group have hosted a post-doc from Herriot Watt to visit our lab and perform experiments. |
Collaborator Contribution | My collaborators have contributed to the grant proposal, new avenues of research, new experiments and calculations. New results are available that will result in new publications. |
Impact | This is a multi-disciplinary collaboration composed of Dr O Cespedes (Leeds -Physics), Dr AI Coldea (Oxford-Physics), Dr G. Teobaldi (Liverpool-Chemistry), Dr J Bos (Herriot-Watt-Chemistry), Dr DA MacLaren (Glasgow-Physics) and funded by EPSRC. Our common work will generate publications in the near future. |
Start Year | 2012 |
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 | UCLA Collaboration |
Organisation | University of California, Los Angeles (UCLA) |
Country | United States |
Sector | Academic/University |
PI Contribution | Experimental study and provision of materials SrAg4As2 |
Collaborator Contribution | Experimental study and provision of materials SrAg4As2 |
Impact | Significant change in the electronic behavior associated with structural distortions in monocrystalline SrAg4As2 Bing Shen, Eve Emmanouilidou, Xiaoyu Deng, Alix McCollam, Jie Xing, Gabriel Kotliar, Amalia I. Coldea, and Ni Ni Phys. Rev. B 98, 235130 - Published 13 December 2018 |
Start Year | 2016 |
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... |