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.

Publications

10 25 50
 
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.
Exploitation Route Our work have been highly cited by our peers working in related research areas. Future potential devices may be develop based on these investigated systems
Sectors Electronics,Energy,Other

URL https://www2.physics.ox.ac.uk/contacts/people/coldeaa
 
Description The staff working on this grant have developed expertise which is now transferable towards their new jobs in materials laboratories focus on developing electronic devices.
First Year Of Impact 2015
Sector Education,Electronics,Energy,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 Academic/University
Country United Kingdom
Start 04/2015 
End 03/2020
 
Description ARPES 
Organisation Diamond Light Source
Country United Kingdom 
Sector Academic/University 
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