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PhD, MSc, & Postdoctoral Opportunities

Post Doctoral Research Staff

The Group currently has no funded post-doctoral positions. If you are planning to apply for an externally funded fellowship (see right) and you would like to discuss the possibility of working with us, please contact one of the permanent members of the group.

PhD Projects

Every year at least one studentship is available for a suitably qualified applicant to join our Group. Early applications for places are strongly encouraged. Details of the projects currently available are given below. For more details of the kind of work carried out by the students in our Group please refer to the PhD current research projects page.

PhD Project Titles - Funded Projects (Note, funding is only available for UK/EU nationals)
Funded Project - Highly frustrated magnetic materials by neutron scattering
Supervisor: Oleg Petrenko

The goal of the project is to experimentally investigate the low-temperatures properties of several highly frustrated magnets using various neutron scattering methods. In the frustrated magnets, competing interactions often cancel each other out creating unusual ground states, such as spin liquid, spin glass and spin ice states. Frustration is often caused by the geometry of the lattice, where the magnetic ions form corner or side-sharing triangles (see Figure 1). Neutron diffraction is the most direct probe of the magnetic structures, while neutron inelastic scattering provides the information on the spectrum of magnetic excitations above the ground states and therefore the strength of the magnetic interactions.

The project will address the important open questions about the nature of the field-induced transitions, the interactions responsible for the selection of a particular magnetic state among many other possibilities and the signatures of the multi-spin correlations.

The project will start with the preparation of the samples, either in a polycrystalline or (much more preferably) a single crystal form. It will then proceed to the in-house characterisation of the samples using x-ray diffraction, magnetisation, resistivity and heat capacity measurements.

The neutron scattering experiments will then be performed at the ISIS Neutron and Muon Source (Rutherford Appleton Laboratory), the Institut Laue- Langevin (Grenoble, France) and other neutron scattering facilities, such as PSI and MLZ. Figure 1. Positions of magnetic ions in Gadolinium Gallium Garnet. The coloured lines show rings of 10 ions, on which a spin wave is localised in a field-induced ferromagnetic state.

The main candidates for the investigations are gadolinium-containing garnets [1], the rare earth tetraborides [2], the zigzag ladder compounds of the SrRE2O4 family [3] as well as the distorted honeycomb-like lattice compounds [4].

We are also constantly looking for new geometrically frustrated systems to synthesise and investigate.

[1] J. A. M. Paddison, O. A. Petrenko et al., Science 350, 179 (2015); N. d'Ambrumenil, O.A. Petrenko et al., Phys. Rev. Lett. 114, 227203 (2015).
[2] D. Brunt, O. A. Petrenko et al., Crystals 9, 211 (2019); Sci. Reps. 8, 232 (2018).
[3] O. A. Petrenko et al., Phys. Rev. B 95, 104442 (2017); Low Temp. Phys. 40, 106 (2014).
[4] H. S. Nair et al., Crystals 9, 196 (2019).


Funded Project - Understanding quantum materials using high magnetic fields and applied pressure
Supervisor: Paul Goddard

Many of today's most interesting, innovative and potentially useful materials display states of matter that seem to be explicable only by applying quantum mechanical models that are on the edge of our current understanding. This is perhaps unsurprising as these quantum materials can be host to a complex medley of ingredients that include many-body interactions between spins, electrons and phonons. The ground states that emerge from this complexity frequently exhibit cooperative properties (superconductivity, Bose-Einstein condensation, charge or spin-order, multiferroicity) or exotic excitations (fractional excitations, solitons, magnetic monopoles, skyrmions, Majorana fermions). Besides the fundamental interest in understanding such materials, there is also the prospect of controlling their properties and putting them to use. Potential applications include efficient electrical power generation, transmission and storage; fast and secure communications; medical imaging and treatment; architectures for processing and caching quantum information; and compact solid-state devices, sensors and actuators. For these reasons, deciphering what causes quantum states of matter to form remains one of the most pressing challenges facing modern physics.

This PhD project aims to advance our knowledge of these states by using magnetic field and pressure to enable a continuous, clean and reversible tuning of quantum interactions, thereby shedding light on the building blocks of quantum materials. The project takes as its starting point recent theoretical and experimental discoveries in the area. In particular, we will focus on a selected series of materials that are on the verge of a phase instability. For example, recently my research team has shown that using molecular-building blocks it is possible to construct near-ideal examples of one and two- dimensional magnets that exhibit some deeply quantum effects in high fields (see Fig.1) [1,3]. We also investigate exotic metallic systems, such as CeOs4Sb12 whose ground state has a most unusual, highly pressure dependent phase diagram governed by proximity to a topological semi-metal state and a quantum critical point driven by applied magnetic field.

Recent examples of quantum materials. (a) The spin-1/2 antiferromagnetic chiral chain [Cu(pyrazine(H2O)4]SbF6H2O. This is a deeply quantum system that is found to display as yet unexplained behaviour in an applied magnetic field [1]. Inset shows a single crystal of the material. (b) Magnetic quantum oscillations (top) observed in ac frequency measurements of the strongly correlated semi-metal CeOs4Sb12. The enhancement of the charge carrier effective mass (bottom) points to a hidden quantum critical point around 20 T [2]. (c) Inelastic neutron scattering on the highly one-dimensional spin-1 chain NiI2(3,5-lutidine)4. The peaks at 0.5 and 0.7 meV show an energy gap developing at low temperature as a direct result of the integer spin of the Ni(II) ions [3].

Taking these systems and others, we will use ultra-high fields and applied pressure to push them through the critical region where the state of matter changes and the inherently quantum effects dominate. Electronic, magnetic and structural properties will be measured as the tipping point is breached and the resulting data compared with predictions of theoretical models. We hope that the results will provide answers to questions of deep concern to modern physics, such how quantum fluctuations, topology and disorder can be used to create states of matter with fascinating and functional properties..

[1] J. Liu, et al., Phys. Rev. Lett. 122, 057207 (2019).
[2] K. Gotze et al., Phys. Rev. B 101, 075102 (2020).
[3] R. Williams et al., Phys. Rev. Res. 2, 013082 (2020).


Other PhD Project Titles
(Please note, that any funding for these projects would only be available for UK/EU nationals)

Chiral and Skyrmionic Magnetic Materials

Supervisor Geetha Balakrishnan, Co-supervisor Martin Lees

The recent discovery of skyrmions in magnetic materials and of their self organisation into a skyrmion lattice together with their potential use for magnetic storage has made skyrmion physics one of the hottest topics in magnetism research.

A PhD studentship is available starting from October 2019 to work on chiral magnets and skyrmionic materials, including materials which have previously been identified to exhibit skyrmionic behaviour, as well as exploring new materials which may exhibit this behaviour. The project will make use of a number of experimental techniques to synthesize the crystals and will encompass the study of the crystals produced through detailed investigations of their structural and magnetic properties. The project will involve several collaborations with research groups both within the UK and Internationally. To complement our in-house studies, there will also be scope for taking part in experiments at international facilities using neutrons, muons and synchrotron radiation.
The project takes place in the context of a wider programme of materials investigation currently underway within the Superconductivity and Magnetism Group in the University of Warwick. Warwick is one of the five consortium universities in the UK National Research Programme on “Skyrmionics: From Magnetic Excitations to Functioning Low-Energy Devices”, funded by EPSRC, UK, involving the universities of Durham, Oxford, Cambridge and Southampton. Industrial partners are also involved.

This is a new, exciting and fast moving field and an ideal project for a strong and enthusiastic student. The student will be enrolled on the Materials Physics Doctorate scheme (go.warwick.ac.uk/MPDOC).

Topological Insulators

Supervisor Geetha Balakrishnan, Co-supervisor Martin Lees

Topological Insulators (TIs) have been hailed as a new state of matter. TIs are materials that are insulating in the bulk, but exhibit special surface states that are conducting and topologically protected-i.e. the spin-orbit coupling in these materials leads to the formation of surface states that cannot be destroyed by scattering or impurities. Following the discovery of topological behaviour in the 2-D HgTe systems, several new 3-D materials exhibiting topological behaviour have been discovered. The 3-D TIs are thought to hold immense potential and have been likened to graphene in their surface electronic properties, with great promise for technological applications in areas such as thermoelectrics, electronics, spintronics and quantum information processing to name just a few.

Although the TIs have gapless edge or surface states that are protected, and an insulating gap in the bulk, most of the 3-D TIs discovered to date are still fairly conducting in the bulk. The challenge has been to create TI materials that are true insulators in the bulk in order to enable the study of their exotic surface states. Materials design and preparation has emerged as being key to the investigation and the discovery of new and better TIs.

The study will involve the synthesis of high quality TIs and characterisation of the bulk properties to understand their importance in influencing the surface states. Emphasis will be placed on the investigation of the structural aspects, information from which will be used to design and fabricate potential materials with TI behaviour. The project will also involve work on several Topological Crystalline Insulators (TCIs), Topological Kondo Insulators as well as TIs that are superconductors, exhibiting a full pairing gap in the bulk and gapless surface states, in analogy with the TIs. Some experimental work on the production and study of new TIs/TCIs in the form of nanomaterials will also be attempted.

The project is part of a new EPSRC funded programme on Topological Insulators. The student will be offered valuable training in the synthesis, in-house characterisation and the use of neutrons and muons at central facilities for the study of the interesting properties exhibited by TIs. The student will also have the opportunity to be involved in several collaborations, both within Warwick (Electron microscopy, Structural studies, NMR and Nanoscience) and with various groups outside Warwick to perform ARPES and other experiments to investigate the exotic surface properties of these materials.

The student will be enrolled on the Materials Physics Doctorate scheme (go.warwick.ac.uk/MPDOC).

Frustration in Magnetic Oxides

Supervisor Martin Lees, Co-supervisor Oleg Petrenko

In simple magnetic materials the magnetic behaviour is usually governed by the strength and sign of the interactions between the magnetic moments in the system. In frustrated magnets the competing interactions between the moments cannot all be satisfied simultaneously.

Studies of frustrated magnetic oxides have resulted in the discovery of some exciting new physics including spin ice and monopoles (see Fig. 1). Many of these breakthroughs have opened new avenues of research, while others have raised important questions that remain unanswered. It is the physics of these systems that will be the focus of this project. For some of our recent work please see Refs. 1 to 3.

planar_exchange_coupling.jpg
In this project, you will use image furnaces to grow high quality single crystals of oxide materials. The structural properties of these frustrated materials will be studied using a suite of state-of-the-art x-ray spectrometers and electron microscopes. You will examine the magnetic properties of these crystals in the laboratory at low temperatures and in high magnetic fields. You will also use a range of neutron scattering and muon spectroscopy techniques at national and international central facilities to investigate the physics of these materials. Fig. 1. Phase diagram as a function of temperature T and the relative strength of the planar and Ising exchange for some pyrochlore titanates. Ho2Ti2O7 and Dy2Ti2O7 are spin ice while Yb2Ti2O7 undergoes a first-order transition from a Coulomb liquid to a Higgs phase of magnetic monopoles [1].

This experimental project will offer an excellent training in many aspects of modern condensed matter physics. The student will be enrolled on the Materials Physics Doctorate scheme (go.warwick.ac.uk/MPDOC).

[1] L.-J. Chang, S. Onoda, Y. Su, Y.-J. Kao, K.-D. Tsuei, Y. Yasui, K. Kakurai, M. R. Lees, Nature Communications 3, 992 (2012).
[2] S. Petit, E. Lhotel, B. Canals, M. Ciomaga Hatnean, J. Ollivier, H. Mutka, E. Ressouche, A. R. Wildes, M. R. Lees, G. Balakrishnan, Nature Physics 12, 746 (2016).
[3] E. Lhotel, S. Petit, M. Ciomaga Hatnean, J. Ollivier, H. Mutka, E. Ressouche, M. R. Lees, G. Balakrishnan, Nature Communications 9, 3786 (2018).

Unconventional Superconductors
Supervisor: Martin Lees, Co-supervisor Geetha Balakrishnan

In conventional superconductors the supercurrents are carried by s-wave Cooper pairs. In unconventional superconductors, the pair wave function may be an odd-parity spin-triplet, or perhaps some mixture of even and odd parity. Unconventional superconductivity may be found in materials with noncentrosymmetric structures, i.e. systems which lack a centre of inversion where parity is no longer a good quantum number, and in materials with strong spin-orbit coupling, e.g. those containing 4d and 5d metals. In this experimental project it will be these two groups of superconductors that will be the focus of your work. The unconventional superconducting properties you will investigate include exotic superconducting gap structures (lines or nodes in the superconducting gap), magnetoelectric effects such as a helical phase and upper critical fields exceeding the Pauli limit, time reversal symmetry breaking, and even topological effects. For some of our work in this area please see Refs. 1-3.

Working in the Superconductivity and Magnetism Group you will learn how to prepare polycrystalline and single crystal samples. The structural properties of the samples will be studied using a suite of state-of-the-art x-ray diffractometers and electron microscopes. You will then examine the normal and superconducting state properties of these materials at low temperatures and in high magnetic fields. As well as experiments in our laboratories, a range of neutron scattering and muon spectroscopy techniques available at national and international central facilities will also be used to investigate the physics of these materials.

This experimental project will offer you an excellent training in many important aspects of modern condensed matter physics. The student will be enrolled on the Materials Physics Doctorate scheme (go.warwick.ac.uk/MPDOC).

[1] R. P. Singh, A. D. Hillier, B. Mazidian, J. Quintanilla, J. F. Annett, D. M. Paul, G. Balakrishnan, and M. R. Lees, Physical Review Letters 112, 107002 (2014).
[2] J. A. T. Barker, D. Singh, A. Thamizhavel, A. D. Hillier, M. R. Lees, G. Balakrishnan, D. M. Paul, R. P. Singh, and Physical Review Letters 115, 267001 (2015).
[3] D. A. Mayoh, A. D. Hillier, K. Götze, D. M.Paul, G. Balakrishnan, and M. R. Lees, Physical Review B 98, 014502 (2018).

Click here for more details of the formal application procedures, the relevant application forms and a postgraduate prospectus. N.B. This information is mounted on the Physics Department web pages outside this Superconductivity and Magnetism site.


MSc Research Projects

We always have places available for suitably qualified self-funded students who would like to work towards an MSc. For more details of the kind of work carried out by the students in our Group please refer to the current postgraduate research projects page.

MSc Project Titles

Topological Insulators: Investigation of the bulk properties of new topological insulators and superconductors.

Supervisor Geetha Balakrishnan

Click here for more details of the formal application procedures, the relevant application forms and a postgraduate prospectus. Note, this information is mounted on the Physics Department web pages outside this Superconductivity and Magnetism site.


Technical Posts

At the moment the Superconductivity and Magnetism Group has no vacancies for Technical Staff.


Useful Links

You may like to view the Warwick University Human Resources Office web page with a listing of all the jobs that are currently available here at the University.

Current vacancies at universities throughout the U.K. are listed on the jobs.ac.uk web site.

PhD projects

Click here to see a more details of the PhD projects available here in the Physics Department at Warwick.


Other external funding opportunities for postdoctoral staff

 

Marie-Curie fellowships (European Union funding)

EU Commission
Click here for more details


Royal Society fellowships

The Royal Society
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 Humboldt Foundation - Feodor Lynen fellowships (for German Post-docs)

closing dates: 10th February, 10th June, and 10th October

Alexander von Humboldt
Click here for more details