DPhil Research Projects 2019/20

Informal enquiries may be directed by email to the relevant potential supervisors. Entry requirements can be found on the Graduate Admissions Website.

The following projects are open for applications for entry in October 2019:

Professor Henry Snaith

All-perovskite multi-junction solar cells

Applications are open currently open for this project.

This studentship is linked to the "prosperity partnership" project between Oxford PV Ltd and the University of Oxford. In this prosperity partnership, we have combined pioneering academic and industrial leaders in perovskite photovoltaics and will develop the underlying materials, science and technology, which will allow us to develop the next generation of multi-junction perovskite solar cells. The ambition of the project is to go well beyond the state-of-the-art, and deliver over 37% efficient triple junction perovskite solar cells, with good long term operational stability. This will be possible through a combined effort of new materials development, fundamental investigations, thin-film device engineering and interface modification, and significant effort on understanding and improving materials and device stability. The DPhil student working on this project will work collaboratively with the Postdocs, Scientist and Engineers, and probe deeply into understanding the photo physical and electronic processes which control optoelectronic operation, and long term stability of the solar cells.

Full details are available by contacting Professor Snaith:

Email: Prof henry Snaith at:
henry.snaith@physics.ox.ac.uk

Applicants interested in the above projects should use the application form which will shortly be available on the Graduate Admissions website.

Applications will be considered as and when they are received and this position will be filled as soon as possible. The course will close on a Friday at a week’s notice. Please check here https://www.ox.ac.uk/admissions/graduate/courses/courses-open-for-studen... for up-to-date information on the closing date.

The following projects are not currently open for applications.

Prof Arzhang Ardavan

Quantum Coherent Phenomena in Molecular Magnets


Figure: A two-qubit device built by tying together individual molecular magnets in a controlled way, with the aim of generating entangled states and hosting simple quantum algorithms.

Molecular magnets are a class of zero-dimensional strongly correlated electron systems exhibiting a highly coherent quantum spin at low temperatures. By varying the molecular structure, properties of the spin such as its moment, anisotropy, etc., can be manipulated in a controlled way, offering a beautiful playground for experiments in quantum magnetism.

This project will investigate ways of exploiting the quantum properties of molecular magnets with a range of objectives. Through close collaborations with chemists who synthesise the materials, we will design structures using molecular spins as qubit candidates. In simple multi-qubit structures, we will use state-of-the-art electron spin resonance equipment to generate entangled states and perform basic quantum information algorithms. We will also develop new ways of measuring electrical transport through single molecules using innovative methods for device construction, and scanning tunnelling microscopy (via collaboration with IBM).
Email Prof Arzhang Ardavan at: arzhang.ardavan@physics.ox.ac.uk.

Dr Richard Berry

Biological Rotary Molecular Motors


Nature DID invent the wheel, at least 3 times! The bacterial flagellar motor is 50 nanometres across, spins at over 100,000 r.p.m. driven by electric current, and propels swimming bacterial cells. ATP-synthase is even smaller, about 10 nm across, consists of two rotary motors coupled back-to-back, and generates most of the ATP - life's "energy currency" - in most living organisms. We are trying to discover how these living machines work. We develop and use a range of methods in light microscopy including ultra-fast particle tracking, magnetic and optical tweezers and single-molecule fluorescence microscopy. Current projects in the lab: measurement of stepping rotation and mechano-sensing in flagellar motors, synthetic biology using ATP-synthase,single-molecule fluorescence microscopy of protein dynamics in bacterial motility and chemotaxis, high-torque magnetic tweezers, templated assembly of flagellar rotors using DNA nanotechnology scaffolds (collaboration with Turberfield group).
More ...

Email Dr Richard Berry at: r.berry1@physics.ox.ac.uk

Prof Stephen Blundell

Negative muons as a new local probe of novel magnetic oxides

Implanted muons give a unique local perspective on quantum materials. By measuring the rotation of the implanted muon spin in the local magnetic field, which in turn results from the dipolar field arising from nearby magnetic moments, one can follow the magnetic order parameter as a function of temperature. If there are a range of muon sites the technique can provide information about the internal magnetic field distribution. Even above the magnetic transition temperature, the measured relaxation of the muon spin can provide information about magnetic fluctuations and spin dynamics. In superconductors the technique is particularly valuable because the measured internal field distribution can allow us to infer the pairing mechanism. This technique is called μSR (muon spin rotation) and research in this area has almost exclusively utilised positive muons. Negatively charged muons have very different properties when implanted in matter and this project will explore a new approach for studying samples using these particles. Since negative muons stop close to atomic nuclei, their sites are well defined and the signal from light atoms such as oxygen is very long-lived. This provides a new route to detecting magnetic fields in highly symmetrical sites inside complex magnets. The experiments will be supported by calculations using a technique we have developed which we call "DFT+mu", density functional theory with an included muon. Collaborative work aimed at advancing the technique which will be carried out with the nearby Rutherford Appleton Laboratory who operate the world's most intense beam of pulsed muons. (Funded by an ISIS Facility Studentship)

Email Prof Blundell at: stephen.blundell@physics.ox.ac.uk.

Prof Andrew Boothroyd

Novel Electronic Order and Dynamics in Crystals


Systems of interacting electrons frequently exhibit subtle forms of order, examples being superconductivity and magnetism. In this project you will investigate electronic order and dynamics experimentally. Neutron and X-ray scattering will be the main techniques used, taking advantage of the new ISIS 2nd target station and the Diamond Light Source, plus other facilities in Europe. A willingness to travel is essential! Magnetic, transport and thermal measurements will be performed in the Clarendon Laboratory, and there is scope for theoretical modelling and numerical analysis. More...
Email Prof. Andrew Boothroyd at: a.boothroyd@physics.ox.ac.uk

Dr Yulin Chen

Topological Insulators - A New State of Quantum Matter

Our group's research interest lies in experimental condensed matter physics: and specifically in understanding the behaviour of electrons in unconventional materials. Recently, we have focused our research activities in the following two directions:

I. Topological quantum matters
a) Topological insulators with better and richer properties
b) Topological Dirac and Weyl Semimetals
c) Topological superconductors
d) Low dimensional thin film and nano-scale topological quantum materials
e) Exploring application potentials of topological quantum materials

II. Research on complex materials with strongly correlated electron system
a) Unconventional superconductors
b) Colossal magneto-resistance (CMR) and other extremely large magneto-resistance (XMR) materials.
c) Heavy fermion systems

In addition, we’re also interested in developing advanced instrumentation that will drive the exploration of critical information on condensed matter systems with new degrees of freedom, such as: Lab, synchrotron and free electron laser based Spin-, time- and angle-resolved photoemission spectroscopy.

For more information of our recent research, please visit our website:
http://www.arpes.org.uk/Publication.html


Figure 1: Surface conduction of topological insulators (A) The spin of electrons on the surface is correlated with their direction of motion (B) The lattice structure of Bi2Te3 and the predicted relativistic "Dirac cone" like electronic structure formed by the surface electrons. (C) The electronic structure measured by angle-resolved photoemission (Figure generated from data in Ref(1)) that confirmed the theoretical prediction and the topological nature of Bi2Te3.

Topological insulators represent a new state of quantum matter with a bulk gap and odd number of relativistic Dirac fermions on the surface (Fig. 1). The bulk of such materials is insulating but the surface can conduct electric current with well-defined spin texture. In addition, the relativistic energy-momentum relationship of electrons in these materials provides a great opportunity to study the physics of relativity in a condensed matter system with the velocity of massless particles about 200 times slower than the light speed in vacuum. The unique properties of the topological insulators make them great candidate for energy and technology applications.

Unlike other materials where the fragile surface states can be easily altered by details in the surface geometry and chemistry, topological insulators are predicted to have unusually robust surface states due to the protection of time-reversal symmetry. These unique states are protected against all time-reversal-invariant perturbations, such as scattering by non-magnetic impurities, crystalline defects, and distortion of the surface itself, and can lead to striking quantum phenomena such as quantum spin Hall effect, an image magnetic monopole induced by an electric charge, and Majorana fermions (whose anti-particle is itself) induced by proximity effect from a superconductor.

Extracting the electronic and structural properties of topological insulators is essential for both the understanding of the underlying physics and potential applications. As a direct method to study the electron band structures of solids, ARPES can yield rich information of the electronic bands of topological insulators, as demonstrated in our recent results on the realization of the large gap single Dirac cone topological insulator Bi2Te3(Ref 1), the insulating massive Dirac fermion state (Ref. 2), and a topological superconductor candidate (Ref.3). For more information, please visit http://www.arpes.org.uk/

[1] Y. L. Chen, et. al., “Experimental Realization of a Three Dimensional Topological Insulator, Bi2Te3” Science, 325, 178 (2009)
[2] Y. L. Chen, et. al., “Massive Dirac Fermion on the Surface of a magnetically doped Topological Insulator” Science, 329, 659 (2010)
[3]. Y. L. Chen, et. al., “Single Dirac Cone Topological Surface State and Unusual Thermoelectric Property of
Compounds from a New Topological Insulator Family”
, Physical Review Letter, 105, 266401 (2010)

Email Dr Yulin Chen at: yulin.chen@physics.ox.ac.uk

Dr Amalia Coldea

Experimental investigation of Electronic Structure of Novel Superconductors Using Angle Resolved Photoemission Spectroscopy

Superconductivity is a unique state of matter with significant potential for practical applications due to the ability of electrons to travel without dissipations in these materials. Superconductivity is an instability of the electronic structure in presence of certain interactions caused either by the lattice, magnetic, charge or orbital fluctuations that cause the electron to pair up as Cooper pairs. Iron-based superconductors are a new class of exciting material that offer a new prospective on the important routes towards high-temperature superconductivity. This project focuses on establishing experimentally the key ingredients that govern the electronic structure and the superconducting state found in different classes of iron-based superconductors in the presence of competing nematic and magnetic ground states. The project will use external parameters to change the electronic structure using applied strain, chemical pressure and in-situ electron and to build up a comprehensive picture of how to enhance superconductivity towards high-temperature regimes. Experiments will be performed both at the Diamond Light Source and at the University of Oxford by complementing state-of-the art high-resolution angle resolved photoemission spectroscopy, with magnetotransport studies as well as theoretical first-principle calculations. A suitable candidate needs to have a good understanding of condensed matter physics and good computing skills as well the ability to work well in an experimental team. This project will be jointly supervised by Dr Amalia Coldea and Dr Timur Kim at the Diamond Light Source.

Exploring the electronic structure and superconductivity of quantum materials under strain

This project will investigate the response of quantum materials, especially iron-based superconductors, to applied lattice strain. The fundamental reason to do this is that in these materials there are many electronic processes that occur simultaneously, which can be difficult to disentangle when looking at the unstressed system alone. One can gain much more information by understanding how elastic lattice distortion, applied through hydrostatic, biaxial, or uniaxial stress, affects the electronic properties of a material. For example, lattice strain may be used to suppress an electronic instability, or to enhance one or more of the processes in the material. One major area of interest in the iron-based compounds, which is likely to be a key part of this project, is electronic nematicity, a form of electronic order which breaks rotational but not translational symmetries. Nematicity may play an important role in high-temperature superconductivity. Uniaxial stress can be used to increase nematic polarisation in a material, by adding to the orthorhombic lattice distortion associated with nematic order.

Measurements to be performed may include quantum oscillations in high magnetic fields of up to 45T and potentially angle-resolved photoemission at the Diamond Light Source. The project also involves the development of high-precision, piezoelectric-driven stress apparatus, for example of a miniaturised stress cell that fits into a high-field magnet and therefore is suitable for students who want to develop their engineering skills along with their scientific skills. A suitable candidate should have a good understanding of condensed matter physics, good experimental and computing skills, and an ability to work well in an experimental team. This project will be jointly supervised by Dr Amalia Coldea at Oxford University, and by Dr Clifford Hicks and Prof Andrew Mackenzie at the Max Planck Institute for Chemical Physics of Solids, in Dresden, Germany.

The student will be expected to spend approximately half of the time in Oxford and half in Dresden.

Tuning electronic ground states and superconductivity of iron-based superconductors under extreme experimental conditions of high magnetic field and applied hydrostatic pressure

Applied hydrostatic pressure is a unique tuning parameter to study the characteristics of a nematic quantum critical point in the absence of long-range magnetic order in a single material and to gives access to the electronic structure and correlations of new magnetic and structural phases. FeSe is an unique superconductor that show a nematic electronic phase in which absence of magnetism at ambient pressure. However, a magnetic phase is stabilized at high pressure and superconductivity is enhanced four-fold. By combining the chemical pressure with the hydrostatic pressure in the series FeSe1-xSx, it is possible to separate the nematic and magnetic phases. This project will aim to understand the evolution of the complex Fermi surfaces and electronic interactions across the nematic phase transitions using applied hydrostatic pressure in different iron-based superconductors. High magnetic field and low temperatures will be used to access directly the Fermi surface by detecting quantum oscillations in different ground states tuned by applied hydrostatic pressure. A suitable candidate needs to have a good understanding of condensed matter physics and good experimental and computational skills as well the ability to work well in an experimental team.

Revealing topological signatures in the electronic behaviour of bulk quantum materials with Dirac dispersion

This is an experimental project combining electronic transport and quantum oscillations to detect unusual signatures of the manifestation of topology in single crystals of quantum materials with Dirac dispersions. The student will perform a series of studies in high magnetic fields and at low temperatures to search for evidence of non-trivial Berry phases and low temperature quantum transport. Studies will be also extended under applied pressure and strain to identify proximity to new toplogical superconducting phase. The work will be combined with first-principle band structure calculations to compare with experiments and disentangle trivial from non-trivial effects. A suitable candidate needs to have a good understanding of condensed matter physics and good computing skills as well the ability to work well in an experimental team.

Developing electronic tunable devices of thin flakes of iron-based superconductors

This project is to explore electronic and topological behaviour of quasi-two dimensional devices based on thin flakes of highly crystalline superconducting iron-based chalcogenides as well as Dirac and Weyl semimetals. The project will involve device preparation and a suite of physical properties measurements to study their electronic properties using high magnetic field and low temperatures. The aim is to search for quantum phenomena as well as for signature of topological matter in these highly tunable quantum material devices. The project will be hosted by the recently funded Oxford Centre for Applied Superconductivity (CfAS) in the Department of Physics. The student will investigate the phase diagrams of novel superconducting thin flake devices under different extreme conditions of high magnetic field, strain and pressure. Experiments using advanced techniques for transport will be performed using high magnetic field facilities available in Oxford and elsewhere. A suitable candidate needs to have a good understanding of condensed matter physics and good computing skills as well the ability to work well in an experimental team.

For more information and specific projects please follow this link

Further queries about these projects should be directed to Dr Amalia Coldea at amalia.coldea@physics.ox.ac.uk

Prof Radu Coldea

Quantum Magnetism and Quantum Phase Transitions

We explore experimentally materials where quantum correlation effects between electrons are important and often lead to novel forms of electronic order or dynamics dominated by quantum effects. Of particular interest is the phenomenon of "quantum frustration", i.e. how quantum systems resolve competing interactions, this is explored in frustrated spin-, orbital- and charge-ordered systems. Another focus is "quantum criticality" when the transition temperature to spontaneous magnetic order can be suppressed by high magnetic fields all the way down to zero temperature, thus realizing a regime where all ~10^23 electron spins in the material fluctuate strongly, but in perfect unison, a new regime for quantum matter that is only now becoming accessible experimentally and we plan to measure directly the quantum spin fluctuations via neutron scattering. The DPhil project will involve a mix of thermodynamic measurements, xray and neutron scattering experiments, data analysis and modelling.
More...
Email Prof Radu Coldea at: r.coldea@physics.ox.ac.uk

Prof Sonia Contera

Magnetically controlled polymeric materials for biomedical applications

We are developing magnetically controlled systems for applications in e.g. cell culture and drug and cell delivery applications and to act as force transducers to interact with living systems.

Electromechanical coupling in neurons

The EPSRC funded Multidisciplinary programme NeuroPulse aims at developing and utilising state-of-the-art modelling approaches for the study of electrophysiological and mechanical coupling in a healthy and mechanically damaged axon, nerve and, eventually, spinal cord and brain white-matter tract. Collaboration with Prof Antoine Jerusalem (Engineering Science Oxford). Two teams of clinical project partners in Oxford and Cambridge will participate in the analysis of the results for direct applications in a clinical setting.

Physical aspects of cryopreservation of living systems

During cryopreservation, cells (e.g. stem cells, sperm, blood), tissues (ovarian tissues, umbilical cord, seeds, plants, fruit), and living organisms (bacteria, animal embryos) are preserved by cooling to sub-zero temperatures. A significant challenge of cryopreservation is to avoid damage caused by the formation of ice crystals during freezing. It is known that when cells are frozen they undergo a ‘‘cold shock'' which leads to mechanical damage to the plasma membrane and leakage of solutes across membranes. This project addresses the fundamental physics of ice formation and the role of biological interfaces and aims at the development of physical methods to increase the viability of frozen living systems. This is part of a new multidisciplinary collaboration OxfordCryo that puts together researchers from Physics, Mathematics, Engineering, Oxford University hospitals Zoology, Philosophy and Law departments, and external partners.

Prof. J.C. Séamus Davis

Visualizing Quantum Matter at the Atomic-Scale

DAVIS GROUP RESEARCH OPPORTUNITIES

Davis Group research concentrates upon the fundamental physics of electronic, magnetic and atomic quantum matter. A specialty is development of innovative instrumentation to allow direct visualization (or perception) of characteristic quantum many-body phenomena at atomic scale. Among the fields of active interest today are:

Capture.PNG

Davis Group plans to operate two suites of ultra-low vibration laboratories, one in Beecroft Building at Oxford University (UK) and the other in the Kane Building at University College Cork (IE). Ours is as single research group conducting scientifically harmonized studies with complementary scientific instruments at Oxford and Cork. The overall objective is to exploit the distinct capabilities and facilities at both laboratories to maximize scientific efficiency.

Our immediate research objectives and associated collaborators include:

• Cooper-Pair Condensates
• Magnetic Monopole Fluids
• Magnetic Topological Insulators
• Topological Kondo Insulators
• Cu/Fe HT Superconductors
• Viscous Electron Fluids
• Macroscopic Quantum Interferometers
• Quantum Microscope Development

Please check here for further details.

Email: Prof J.C. Séamus Davis at: jcseamusdavis@gmail.com

Prof John Gregg

Spin Electronics

This group has three projects to recruit for this year;

1/ Spin Current Hopping in microwave-pumped Spintronics
2/ How to make and characterise Squeezed Magnons
3/ Studies in Spintronic Magnetism:

Methode Electronics make torque sensors for industrial and automotive application the operating principle of which is based on the magnetoelastic effect in ferromagnetic steels. These are a successful and lucrative product: however their competitiveness would benefit from improvements in a number of areas. Specifically, in order to allow them to function more reliably in magnetically noisy environments, they should ideally exhibit a larger signal field per unit strain. There are also some spurious signal issues attaching to nonuniformities in the sensor magnetisation profile. The project will address these various issues using a combination of X-ray characterisation, magnetometry, Kerr microscopy, radiofrequency sputtering, chemical implantation of selected rare earth impurities and micromagnetic modelling.

Full details are available by contacting Professor Gregg:

Email: Prof John Gregg at:
j.gregg1@physics.ox.ac.uk

Prof John Gregg and Dr Alexy Karenowska

Using Magnons for Renewable Energy Harvesting

This project is led by Professor John Gregg and Dr Alexy Karenowska from the Spintronics group. For further details, please contact Prof Gregg or Dr Karenowska.

Email: Prof John Gregg and Dr Alexy Karenowska at:
j.gregg1@physics.ox.ac.uk and A.Karenowska@physics.ox.ac.uk

Prof Laura Herz

Charge generation dynamics in novel materials for solar cells

PVproject2_0.png

Metal halide pervoskites have emerged as an extremely promising photovoltaic (PV) technology due to their rapidly increasing power conversion efficiencies (PCEs) and low processing costs. Surprisingly, many of the fundamental mechanisms that underpin the remarkable performance of these materials are still poorly understood. Factors that influence the efficient operation of perovskite solar cells include electron-phonon coupling, charge-carrier mobility and recombination, light emission and re-absorption, and ion migration.

During this project we will advance the efficiencies of perovskite solar cells by gaining an understanding of fundamental photon-to-charge conversion processes using a combination of ultra-fast optical techniques, e.g. photoluminescence upconversion and THz pump-probe spectroscopy. These studies feed directly into collaborative efforts aimed at addressing remaining challenges in the in the creation of commercially available perovskite solar cells e.g. stability, band-gap tunability, lead-free perovskites, trap-free materials, material morphology control and alternative device structures. The project will be part of active collaboration with researchers working on solar cell fabrication within Oxford and the UK.

Applications for this project can be submitted through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics - see http://www.admin.ox.ac.uk/postgraduate/apply/ for more information. Informal enquiries may be directed by email to Prof. Laura Herz at l.herz@physics.ox.ac.uk. Some useful information on funding for International Postgraduate Students may be found here.

Transitions from quantum confined to fully delocalized electronic states in semiconductor nanocrystal assemblies

Nanocrystal_0.jpg

The last decade has seen rapid progress in the fabrication and assembly of nanocrystals into thin layers of semiconducting material. Such systems may allow facile deposition of high-quality inorganic semiconductor layers through simple and scalable protocols such as ink-jet printing. However, these procedures raise fundamental questions on the nature of charge transport through such layers. While in sufficiently small nanocrystals, quantum confinement leads to the formation of discrete electronic layers that may exhibit "atom-like", energetically discrete states, increasingly electronic coupling between nanocrystals may induce the formation of mini-bands or bulk-like continuum states.

In this project, we will explore such transitions between fundamentally different regimes of electronic coupling and charge transport. We will spectroscopically investigate nanocrystal networks made of established lead chalcogenide inorganic semiconductors, but also explore more recently developed metal halide perovskite colloid materials. These studies will be interesting not only from a fundamental point of view, but also allow for development of such systems in light-emitting photovoltaics or transistor devices.

Applications for this project can be submitted through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics - see the official Graduate Application Guide for more information. Informal enquiries may be directed by email to Prof. Laura Herz at laura.herz@physics.ox.ac.uk. Some useful information on funding for International Postgraduate Students may be found here.

Energy and Charge Transfer in Biomimetic Light-Harvesting Assemblies

Nanorings2_0.png

Photosynthetic organisms use arrays of chlorophyll molecules to absorb sunlight and to transfer its energy to reaction centers, where it is converted into a charge gradient. These processes are remarkably fast and efficient, because the excited states are coherently delocalized over several chlorophyll units. For natural scientists striving to create new molecular light-harvesting materials for applications such as photovoltaics, the designs nature has invented for us are fantastic templates to learn from. This project will explore energy transfer within and between large porphyrin nanorings that directly mimic natural light-harvesting chlorophyl ring assemblies. By creating interfaces with electron-accepting molecules we aim to create light-harvesting layers that rival their natural counterparts in photon conversion efficiency. This project offers exciting possibilities for work in a new interdisciplinary area of research in collaboration with Prof Harry Anderson at the University of Oxford.

This project allows the exploration of physical phenomena in the increasingly popular area of solution-processed and nanostructured semiconductors, and offer a high degree of training in the elegant and versatile techniques of femtosecond optical spectroscopy.

Applications for this project can be submitted through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics - see the official Graduate Application Guide for more information. Informal enquiries may be directed by email to Prof. Laura Herz at laura.herz@physics.ox.ac.uk. Some useful information on funding for International Postgraduate Students may be found here.

Prof Laura Herz with Prof Michael Johnston

Pump-push-probe spectroscopy for identification and elimination of trap states in hybrid perovskites

Hybrid metal halide perovskites are promising semiconductors for next-generation solar cells now achieving power conversion efficiencies in excess of 22%. However, perovskite cells currently still suffer from sub-bandgap trap states that can act as non-radiative recombination centres, reducing device efficiencies. While the presence of traps in these materials has been inferred from charge-carrier recombination kinetics, their causes and nature are still largely unknown. Computational simulations have predicted the energies of specific point defects, however, matching experimental evidence for specific trap depths is more elusive.

This project will address this issue by implementing a new spectroscopic technique, optical-pump-THz-probe-IR-push transient photoconductivity spectroscopy, to monitor detrapping processes that are stimulated by a short laser pulse whose photon energy is matched to the trap depth. Standard optical-pump-THz-probe techniques already in operation will be extended by a third pulse of tunable photon energy that is used to "push" charges from trap states back into the conduction or valence bands. We will build on the resulting trap identification to develop processing protocols to remove specific hurdles to the adoption of perovskite as photovoltaic light-harvesters. We will target lead-free tin perovskites that currently exhibit dominant defect-related charge recombination, and mixed-halide perovskites for silicon tandems that suffer from trap-mediated halide segregation under illumination.

This project is supervised by Prof Laura Herz and Prof Michael Johnston in association with the EPSRC Centre for Doctoral Training in Plastic Electronics for start in October 2018.

Enquiries may be directed by email to Prof Laura Herz at laura.herz@physics.ox.ac.uk and Prof Michael Johnston at michael.johnston@physics.ox.ac.uk

Prof Thorsten Hesjedal

Magnetic Skyrmionics

Topology treats higher-dimensional geometrical properties of matter that cannot be captured by symmetries.
Nowadays, condensed matter physicists become more and more aware of the fundamental implications of a material’s topological properties. The largely unexplored magnetic skyrmions carry rich topological physics and hold the promise of future applications in information technology.

This is an experimental project dedicated to the exploration and study of novel, low-dimensional skyrmion-carrying materials. It is part of the UK-wide, EPSRC-funded national research program into Skyrmionics, designed to achieve a step-change in our understanding of skyrmions in magnetic materials and engineer them towards application. A detailed description of the research topics and institutions involved can be found at http://www.skyrmions.ac.uk.

Email Prof Thorsten Hesjedal at: thorsten.hesjedal@physics.ox.ac.uk

Selected group publications on Skyrmionics:

[1] Zhang, S. L.; van der Laan, G.; Hesjedal, T.; Direct experimental determination of spiral spin structures via the dichroism extinction effect in resonant elastic soft x-ray scattering, Phys. Rev. B 96, 094401 (2017)

[2] Zhang, S. L. et al., Realisation and observation of room temperature helimagnetism in FeGe thin films, Scientific Reports 7, 123 (2017)

[3] Zhang, S. L.; van der Laan, G.; Hesjedal, T.; Direct Determination of the Topological Winding Number, Nature Commun. 8, 14619 (2017)

[4] Figueroa, A. I.; Zhang, S. L.; et al.; Strain in epitaxial MnSi films on Si(111) in the thick film limit studied by polarization-dependent extended x-ray absorption fine structure; Phys. Rev. 94, 174107 (2016)

[5] Zhang, S. L.; Bauer, A.; Berger, H.; et al., Resonant elastic x-ray scattering from the skyrmion lattice in Cu2OSeO3, Phys. Rev. B 93, 214420 (2016)

[6] Zhang, S. L.; Bauer, A.; Burn, D. M.; et al, Multidomain Skyrmion Lattice State in Cu2OSeO3, Nano Lett. 16, 3285-3291 (2016)

[7] Zhang, S. L.; Chalasani, R.; Baker, A. A.; et al., Engineering helimagnetism in MnSi thin films, AIP Adv. 6, 015217 (2016)

[8] Lancaster, T.; Xiao, F.; Salman, Z.; et al., Transverse field muon-spin rotation measurement of the topological anomaly in a thin film of MnSi, Phys. Rev. B 93, 140412 (2016)

[9] Lancaster, T.; Williams, R. C.; Thomas, I. O.; et al., Transverse field muon-spin rotation signature of the skyrmion-lattice phase in Cu2OSeO3, Phys. Rev. B 91, 224408 (2015)

[10] Zhang, Shilei; Baker, Alexander A.; Komineas, Stavros; et al., Topological computation based on direct magnetic logic communication, Sci. Rep. 5, 15773 (2015)

Angle-Resolved Photoelectron Spectroscopy (ARPES) Studies on Novel, Functional Materials Grown by Molecular Beam Epitaxy (MBE)

Angle-Resolved Photoelectron Spectroscopy (ARPES) is one of the key techniques for studying strongly correlated metallic materials. It can directly visualise the electronic band structure and Fermi surface, measure electron correlations and interactions with quasiparticles, such as phonons and magnons in the material. ARPES is extremely successful for the study of layered materials, where the required atomically clean surface is produced by cleavage and beamline I05 at Diamond Light Source (http://www.diamond.ac.uk/I05) is one of the best stations worldwide for such research (for a list of recent high-profile publications see http://www.diamond.ac.uk/Beamlines/Surfaces-and-Interfaces/I05/Publicati...).

A large number of highly relevant functional materials are, however, not layered in their nature, and the best quality samples can be grown by molecular beam epitaxy (MBE). In this case the samples have to be moved from MBE to the ARPES measurement station all in ultrahigh vacuum (UHV). The MBE [1] has proven its worth in conjunction with ARPES in studies of rock-salt structure doped EuO at variable doping [2].

Further characterisation of the thin films will be carried out either in-situ, such as x-ray photoelectron spectroscopy, or ex-situ, such as x-ray diffraction, electronic transport measurements or the study of their magnetic properties. The student will be based at the Harwell Campus (http://harwellcampus.com/). The outcome of this research will be world-class data on novel functional materials that will allow interesting conclusions to be published in high impact journals.

This project will be jointly supervised by I05’s principle beamline scientist, Dr. Cephise Cacho, and Prof. Thorsten Hesjedal. It will be partially RCUK funded, and so is restricted to applicants with a Home/EU fee status.

References:

[1] A. A. Baker, W. Braun, G. Gassler, S. Rembold, A. Fischer, T. Hesjedal, "An ultra-compact, high-throughput molecular beam epitaxy growth system”, Rev. Sci. Instrum. 86, 043901 (2015) - http://scitation.aip.org/content/aip/journal/rsi/86/4/10.1063/1.4917009

[2] J. M. Riley, F. Caruso, C. Verdi, L. B. Duffy, M. D. Watson, L. Bawden, K. Volckaert, G. van der Laan, T. Hesjedal, M. Hoesch, F. Giustino & P. D. C. King, “Crossover from lattice to plasmonic polarons of a spin-polarised electron gas in ferromagnetic EuO”, Nature Communications 9, 2305 (2018) - https://www.nature.com/articles/s41467-018-04749-w


Figure: Schematic view of the UHV station HR-ARPES, including the ARPES instrument on the right and the mu-MBE growth chamber and characterisation facility on the left.

Email Prof Thorsten Hesjedal at: thorsten.hesjedal@physics.ox.ac.uk

T-REXS – Taking a Bite out of Magnetic Skyrmions

The experimental observation of magnetic skyrmions, i.e., a two-dimensional topological spin state, has laid the foundation for a new research field. The non-trivial geometrical nature of magnetic skyrmions, such as their chiral and topological properties, has lead to significant novel physical effects, e.g., emergent electromagnetism, monopole dynamics, non-reciprocal spin-wave dispersion, etc. Tremendous research efforts have been dedicated to the understanding of the underlying physics, as well as developing ideas for the exploitation.

The focus of this project is to unravel the mystery of novel skyrmion systems by performing transmission resonant elastic x-ray scattering (T-REXS). The recent development of T-REXS has proven to be the ideal tool for studying the complex magnetic structures in thin films, giving unambiguous results compared with other magnetic characterization techniques. We will explore novel magnetic skyrmion systems, e.g., antiskyrmions in the Heusler alloys, and determine their exact structure. This will open the door for exploring topological thin film physics, paving the road towards future applications in information technology.

This is an experimental project dedicated to the study of novel skyrmion-carrying materials by synchrotron-based scattering techniques. This project involves the groups of Prof Stuart Parkin at the MPI in Halle and Prof Thorsten Hesjedal in Oxford.

The project is also tied into the UK-wide, EPSRC-funded national research program into Skyrmionics, designed to achieve a step-change in our understanding of skyrmions in magnetic materials and engineer them towards application. A detailed description of the research topics and institutions involved can be found at http://www.skyrmions.ac.uk.

For further questions, email Prof Thorsten Hesjedal (thorsten.hesjedal@physics.ox.ac.uk)

Selected group publications on Skyrmionics:
[1] Zhang, S. L.; van der Laan, G.; Hesjedal, T.; Direct experimental determination of spiral spin structures via the dichroism extinction effect in resonant elastic soft x-ray scattering, Phys. Rev. B 96, 094401 (2017)
[2] Zhang, S. L. et al., Realisation and observation of room temperature helimagnetism in FeGe thin films, Scientific Reports 7, 123 (2017)
[3] Zhang, S. L.; van der Laan, G.; Hesjedal, T.; Direct Determination of the Topological Winding Number, Nature Commun. 8, 14619 (2017)
[4] Figueroa, A. I.; Zhang, S. L.; et al.; Strain in epitaxial MnSi films on Si(111) in the thick film limit studied by polarization-dependent extended x-ray absorption fine structure; Phys. Rev. 94, 174107 (2016)
[5] Zhang, S. L.; Bauer, A.; Berger, H.; et al., Resonant elastic x-ray scattering from the skyrmion lattice in Cu2OSeO3, Phys. Rev. B 93, 214420 (2016)
[6] Zhang, S. L.; Bauer, A.; Burn, D. M.; et al, Multidomain Skyrmion Lattice State in Cu2OSeO3, Nano Lett. 16, 3285-3291 (2016)
[7] Zhang, S. L.; Chalasani, R.; Baker, A. A.; et al., Engineering helimagnetism in MnSi thin films, AIP Adv. 6, 015217 (2016)
[8] Lancaster, T.; Xiao, F.; Salman, Z.; et al., Transverse field muon-spin rotation measurement of the topological anomaly in a thin film of MnSi, Phys. Rev. B 93, 140412 (2016)
[9] Lancaster, T.; Williams, R. C.; Thomas, I. O.; et al., Transverse field muon-spin rotation signature of the skyrmion-lattice phase in Cu2OSeO3, Phys. Rev. B 91, 224408 (2015)
[10] Zhang, Shilei; Baker, Alexander A.; Komineas, Stavros; et al., Topological computation based on direct magnetic logic communication, Sci. Rep. 5, 15773 (2015)

Typical TREXS sample which was prepared by focused ion beam milling.

Dr Roger Johnson

Interplay between spin and electronic subsystems in complex oxides

The relationship between crystal structure and the physical properties of materials is a central topic of condensed matter physics. Modern experimental techniques that exploit x-ray, electron and neutron diffraction at large-scale central facilities, combined with advanced computational tools, have allowed researchers to study crystal structures with unprecedented precision, bringing the topic to a highly quantitative level. Precise measurements of structural distortions at phase transitions, and their evolution and interactions, offer a unique opportunity to understand fundamental structure-properties relationships, as well as enabling the design of materials with controlled properties.
Our research programme is focused on revealing the physical interplay between spin and electronic subsystems in complex oxides of transition and rare-earth metals, which exhibit a broad variety of magnetic and structural phenomena including ferroelectricity, spin and orbital ordering (Figure 1), as well as metal-to-insulator transitions. This project will involve a comprehensive study of structural and physical properties of new magnetic materials with competing electronic degrees of freedom. Furthermore, it is expected that these novel materials will exhibit rich phase diagrams, easily tuned by light chemical doping and external perturbations such as hydrostatic pressure, magnetic field, or temperature.
The DPhil student will gain a broad experience in experimental methods underpinning condensed matter physics, with particular focus on diffraction techniques performed at large-scale facilities such as ISIS, the UK neutron and muon source, ILL, the European reactor neutron source, and the Diamond synchrotron light source. Data analysis and interpretation will be based upon advanced tools of physical crystallography including the representation of conventional space groups and superspace groups to describe modulated crystal and magnetic structures. This project will therefore form a strong and universal background for independent research in condensed matter physics.

Interplay between spin and electronic subsystems in complex oxides

For more information contact Dr Roger Johnson: roger.johnson@physics.ox.ac.uk

Dr Roger Johnson and Prof Paolo Radaelli

Magneto-orbital physics of novel manganese oxides

The cooperative interactions of electrons in a crystal lattice can give rise to long-range ordering of charge, orbital and spin electronic degrees of freedom. Not only are such states of fundamental physical interest, but they also give rise to technologically important materials properties such as ferromagnetism, ferroelectricity, colossal magnetoresistance, and metal-to-insulator transitions – to name but a few. Furthermore, the different orders can be intimately linked, allowing in special cases the cross coupling of properties. The manganites – crystalline materials containing manganese and oxygen – are now considered to be textbook examples of charge, orbital, and magnetically ordered systems, owing largely to the electronic flexibility of the manganese ion and an ideal bonding geometry [1]. In our group, we recently focussed our research effort on quadruple-perovskite manganites [2-6]. This relatively new family of compounds significantly extends the phenomenology observed in the canonical single perovskites, including completely different forms of ordering such as magneto-orbital helices (Figure 1) [3,5]. The key question is whether there is a general unifying principle connecting all these different types of charge, magnetic and orbital ordering, in both canonical and novel compounds. Answering this question requires:
• Exploring complex magnetic states that arise due to interactions between rare-earth and transition metal ions.
• Manipulating the orbital states of manganese ions through direct isovalent cation substitution or indirect electron doping.
• Altering the metallic character of the compounds from strongly metallic to strongly insulating through manipulation of structural distortions.
• Investigating the role of strong spin-orbit coupling.

Johnson and Radaelli -Manganites Project GRAPHIC.docx__2_0.png

This EPSRC-funded DPhil project will give the successful candidate the opportunity to develop this line of research in different directions, including:
• Materials discovery (bulk and thin film).
• Development of laboratory-based characterisation techniques.
• Large-scale experiments with fully quantitative data analysis.

This project is likely to involve a combination of experimental techniques, such as:
• Elastic neutron scattering. We will perform experiments on bulk and thin film samples predominantly at the ISIS facility at Rutherford Appleton Laboratory.
• X-ray scattering, including resonant and non-resonant magnetic X-ray diffraction with hard and soft X-rays. We run state-of-the-art laboratory instrumentation in the Clarendon Laboratory, but we perform most of our high-end experiments at the Diamond Light source.
• Dielectric and transport measurements. One of our specialities is to perform measurements of ferroelectricity in extremely high magnetic fields (up to 65 T – a record in the UK), using the pulsed-magnetic-field facility in the Clarendon Laboratory, but a complete set of more standard measurements is also available.
• Advanced microscopy. We employ spectral microscopy (PEEM) at Diamond, Magnetic Force Microscopy (MFM) and the Magneto-Optical Kerr Effect to image magnetic domains.

For more information contact Dr Roger Johnson: roger.johnson@physics.ox.ac.uk.
Supervisor: Dr Roger Johnson roger.johnson@physics.ox.ac.uk
Co-Supervisor: Prof Paolo Radaelli paolo.radaelli@physics.ox.ac.uk

[1] D. I. Khomskii, “Transition Metal Compounds”, Cambridge University Press (2014).
[2] R. D. Johnson et al., Physical Review Letters 108, 067201 (2012)
[3] N. J. Perks et al., Nature Communications 3, 1277 (2012)
[4] K. Cao et al., Physical Review B 91, 064422 (2015)
[5] R. D. Johnson et al, Physical Review B 93, 180403(R) (2016)
[6] R. D. Johnson et al., Physical Review B 96, 054448 (2017)

Prof Michael Johnston

Semiconductor Nanowire-Based Solar Cells

III-V nanowires, such as GaAs and InP nanowires, are high aspect ratio cylinders of crystalline inorganic semiconductor, typically with diameters of a few tens of nanometres and lengths of several microns. These novel nanomaterials offer outstanding potential as nano-components of future electronic and optoelectronic devices, and are especially promising candidates for the light absorbing and charge transporting elements of solar cells. Nanowire-based solar cells could be produced at a fraction of the cost of conventional solar cells, and offer the possibility of unprecedented energy conversion efficiencies. This project will involve the fabrication of novel nanowire-based solar cells and studying charge dynamics in these devices using terahertz spectroscopy.
Email Prof Michael Johnston at m.johnston1@physics.ox.ac.uk

To apply for this project you need to submit an application through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics - see http://www.admin.ox.ac.uk/postgraduate/apply/ for more information. If you are an international student there are a range of funding opportunities available to you.

THz Conductivity of Graphene and Graphene-Like Materials


Two-dimensional nano-materials such as graphene are currently the platform for fascinating fundamental science and have the potential to become the building blocks for a new era of fast, low-cost electronics. These materials are already inspiring new device concepts for applications including photovoltaics, sensing, high-speed communications and computing. However at present the electronic properties of many of these new materials are poorly understood, which severely limits the realisation of these electronic devices. Furthermore, nano-materials have a particularly bright future in ultra-high (THz) frequency electronic devices, yet to date their properties have almost exclusively been studied only at low frequencies. This project will develop non-contact tools to measure the electronic properties of nano-materials to frequencies well in excess of the operating frequency of the fastest electronic devices available today.
Email Prof Michael Johnston at m.johnston1@physics.ox.ac.uk

To apply for this project you need to submit an application through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics - see http://www.admin.ox.ac.uk/postgraduate/apply/ for more information. If you are an international student there are a range of funding opportunities available to you.

Terahertz Conductivity of Semiconductor Nanostructures and Devices

As semiconductor devices become faster and smaller it is increasingly important to understand the fundamental nature of charge carrier dynamics in these systems on a sub-picosecon d timescale. Conventional electronic transport and magneto-transport methods are incapable of measuring dynamics on such short time scales. However, "Optical Pump, Terahertz Probe Spectroscopy (OPTHzP)" is a new non-contact technique that allows such measurements to be performed with a femtosecond resolution, thereby revealing novel ultrafast physical processes. When fully understood such processes have the potential be utilised in future generations of electronic devices. This project will make use of the state-of-the-art OPTHzP systems in the Oxford Terahertz Photonics group to help understand charge dynamics in novel semiconducting nanostructures, including semicondutor nanowires (lower Figure), carbon nanotubes and porous InP.

Further Reading:
Our recent study of ultrafast conductivity in GaAs nanowires [more]
Our THz study of polymer field effect transistors [more]
A description of the carrier dynamics model that has been developed in the group [more]
Email Prof Michael Johnston at m.johnston1@physics.ox.ac.uk

To apply for this project you need to submit an application through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics - see http://www.admin.ox.ac.uk/postgraduate/apply/ for more information. If you are an international student there are a range of funding opportunities available to you.

Prof Achillefs Kapanidis

Fighting antibiotic resistance via nano-scale imaging of gene machines


Antibiotic resistance of bacteria is one of the major health challenges the world faces today, driven by overuse of our current antibiotic arsenal. To overcome this massive challenge, there is an intense effort to find new antibiotics and to understand how existing antibiotics work. In the past few years, we have been contributing to this field by developing single-molecule fluorescence imaging methods to study the function of the protein RNA polymerase, responsible for copying DNA into messenger RNA (a process known as “gene transcription”); this protein is also a major target of antibiotics.

Our current efforts focus on watching the nano-scale dynamics of RNA polymerase in real-time to identify new steps in transcription that can act as antibiotic targets, and to understand how existing and new antibiotics exert their function. These efforts depend on the ability to detect single molecules of RNA polymerase as they operate on DNA fragments that resemble expressed genes.

The project will involve single-molecule imaging and microscopy, measurements of 1-10 nm distances within transcription complexes (see Figure) based on dipole-dipole interactions between dyes attached to specific sites, molecular modelling, and advanced signal processing.

For more information, look at our website, or email Prof Achillefs Kapanidis at a.kapanidis1@physics.ox.ac.uk
To apply for this project you need to submit an application through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics – see http://www.ox.ac.uk/admissions/graduate/applying-to-oxford for more information.

Super-resolution imaging of gene expression in living cells

During the past few years, a new family of microscopy methods is revolutionizing biology and medicine. These methods, known as super-resolution fluorescence imaging, rely on ingenious ways that circumvent the resolution limit imposed by the diffraction of light; the potential of these methods was recognized in the award of the 2014 Nobel Prize in Chemistry to three prominent physicists. Many of these methods rely on detecting single fluorescent molecules, and are known as single-molecule fluorescence microscopy, or simply localization microscopy. Localization microscopy bypass the diffraction limit by our ability to localize a fluorescent molecule with a precision up to 100-fold better than the width of its point-spread function (PSF; see figure). Provided that sufficient photons are collected, we can localize single fluorescent dyes with ~1 nm precision.

Using our extensive experience in localization-based super-resolution imaging, we study the 3-D organization and diffusion profile of DNA-binding proteins in single bacterial cells (see Figure at far right for detection of DNA polymerases in single bacteria). We are interested in relating the information regarding the transcription machinery in vivo with quantitative models of transcription. We are also interested in understanding how DNA binding proteins combine 1-D and 3-D diffusion to find their targets in cells and characterize the processes involved.

The project will involve single-molecule imaging and microscopy, single-molecule tracking in living bacteria based on localization microscopy, molecular modelling, and advanced signal processing.

For more information, look at our website, or email Prof Achillefs Kapanidis at a.kapanidis1@physics.ox.ac.uk
To apply for this project you need to submit an application through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics – see http://www.ox.ac.uk/admissions/graduate/applying-to-oxford for more information.

DNA biosensors for detecting pathogenic bacteria and viruses


DNA is an extremely versatile material for build novel biosensors; molecules can be encoded with binding sites specific for proteins of interest, or for other nucleic acids (DNA/RNA), and can be easily modified to contain useful chemical groups such as fluorophores, biotin or quantum dots. Employing self-assembly properties of DNA, one can also design topological features to create different 2- or 3-dimensional shapes of sizes that can provide exquisite molecular recognition. This additional layer of freedom allows considerable flexibility when designing biosensors.

Our lab develops biosensors for the single-molecule detection of DNA-binding proteins (see Figure), nucleic acids, and viral particles. We are currently interested in detecting pathogenic bacteria (using E.coli as a model system) and viruses (using the influenza virus as a major pathogen target).

The project will involve design of DNA biosensors, single-molecule imaging and microscopy, chemical treatment of bacteria and viruses, theoretical modelling, and advanced signal processing.

For more information, look at our website, or email Prof Achillefs Kapanidis at a.kapanidis1@physics.ox.ac.uk
To apply for this project you need to submit an application through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics – see http://www.ox.ac.uk/admissions/graduate/applying-to-oxford for more information.

Development of portable single-molecule imaging


We have recently developed a revolutionary novel portable optical microscope (“NanoImager”; see Figure) for advanced single-molecule imaging. The NanoImager is based on single-molecule fluorescence, which is the most popular single-molecule detection method, especially in vivo; single-molecule fluorescence has elucidated many biological mechanisms, allowed sub-diffraction cellular imaging (see Figure) and enabled biosensing applications such as next-generation DNA sequencing. The NanoImager has a highly efficient and robust optical/mechanical design that improves stability and substantially reduces complexity and size; these unique features offer a platform that can address large needs in research, diagnostics, and chemical analysis, and spark new applications in many sectors.

We have openings to work on further extensions of the NanoImager that will make it portable, increase its modes of operation (3D imaging, single-molecule tracking, detection of cells in suspension), interface it with microfluidics, and increase the molecular throughout. This project can be combined with the DNA biosensor project offered by the same group.

For more information, look at our website, or email Prof Achillefs Kapanidis at a.kapanidis1@physics.ox.ac.uk
To apply for this project you need to submit an application through the University's Postgraduate Admissions Programme to the Department of Condensed Matter Physics – see http://www.ox.ac.uk/admissions/graduate/applying-to-oxford for more information.

Dr Alexy Karenowska

Quantum Magnon Spintronics

Spintronics is the area of research dedicated to the study of how ‘spin’—the quantum mechanical currency of magnetism—can be used realize new types of information transport, storage, and processing system which surpass the capabilities of those currently found in our computers and other electronic devices.
The field of magnonics is the area of magnetics dedicated to the science of quasi-particles known as magnons. In certain magnetic systems, magnons are able to play the role of microscopic spin-carrying tokens which can be generated and transmitted over relatively long distances (up to centimetres) and at high speed (many tens of kilometres per second). Magnon spintronics, magnonics’ emerging sister discipline, is concerned with structures and devices which involve the passing of spin-information between magnons and electrons, the familiar workhorses of conventional electronics.
As appreciation of the interplay between magnonic and electronic spin-transport deepens, so excitement surrounding its possible contribution to next-generation information technology heightens. To date however, work in magnonics and magnon spintronics has focused on the study of room-temperature magnon and magnon/electron systems in the classical limit. As a result, the field of experimental quantum measurement and information processing has yet to explore what the magnonic theatre has to offer.
This project will involve working on the development of novel experiments for the investigation of magnonics and magnon spintronics at the quantum level. In particular, its goal will be to take some of the first steps towards accessing the new physics and technological opportunity at the interface between magnonic and magnon spintronic systems, and the techniques of contemporary quantum measurement and information processing.
Email Dr Alexy Karenowska at a.karenowska@physics.ox.ac.uk

Dr Karenowska has a further project, which is joint project with Prof John Gregg. Please see above 'Prof John Gregg and Dr Alexy Karenowska.

Dr Peter Leek and Dr. Boon Kok Tan

Superconducting Parametric Amplifier for Astronomy and Quantum Computing

The emergence of a new type of amplifier technology, the superconducting parametric amplifiers (SPAs), had drawn considerable attention from the astronomical and quantum computing communities. This is because SPAs can achieve quantum-limited sensitivity over a very broad bandwidth. They are compact, easy to fabricate with planar circuit technology, have ultra-low heat dissipation, and can be integrated directly with other detector circuits. Their performance is far superior to the state-of-the-art cryogenic low noise amplifier used currently in astronomy and quantum computing experiments. These devices therefore can revolutionise ultra-sensitive instrumentation in astronomy and quantum information technologies, from microwave to sub-millimetre (sub-mm) wavelengths. In particular, they can be used as readout amplifiers to improve the heterodyne receiver sensitivity significantly, and enable the construction of large bolometric arrays as a result of the negligible dissipation. Their large bandwidth, high power handling and quantum-limited noise performance will have profound effect on quantum computing architecture and improve the fidelity to process hundreds of quantum bits (qubit), opening up the possibility of building a practical quantum computer.

In this project, the student will start by studying the theoretical background and develop his/her own simulation code to model the SPA, along with learning to use commercial electromagnetism software to design the amplifiers. The student will then have the chance to get involve in the fabrication of the devices using state-of-the-art clean room facilities, either here in Oxford, or with our other collaborators (Paris, Chalmers, Cambridge etc). The student will also learn how to use sub-Kelvin cryogenics system and other experimental techniques, for measuring the performance of the amplifiers. In particular, the student will investigate the amplifier sensitivity and gain dependence on bath the temperature and on the losses of superconducting materials. Finally, the student will integrate the amplifier into an existing astronomical receiver/quantum computing receiver and assess the impact on the receiver performance.

The Superconducting Quantum Detectors Group in Oxford have a well-equipped laboratory, with all the required instruments to perform the design and test of the amplifiers. He/she will also be assisted by an experienced technician, working along with post-docs in the group, with the support from the electronics, mechanical and photo-fabrications expertise in Oxford Physics. There is a possibility to get involved in an astronomical observation project as well (with Prof. Dimitra Rigopoulou), including performing the observation using existing mm/sub-mm telescopes.

Find more about our research group here https://www2.physics.ox.ac.uk/research/millimetre-and-thz-detector-devel... .

Email Dr Boon Kok Tan at boonkok.tan@physics.ox.ac.uk

Email Dr Dr Peter Leek at peter.leek@physics.ox.ac.uk

Prof Robin Nicholas and Dr Moritz Riede

Graphene and carbon nanotube based PV electrodes

Both graphene and carbon nanotubes have very high electrical conductivities and mechanical strength, which makes them ideally suited for use as electrodes for flexible solar cells, replacing costly and brittle ITO and FTO. Over the past years, we have been successfully working on these kinds of electrodes, investigating how to use graphene monolayer electrodes, graphene flakes and carbon nanotubes as both electron and hole collecting layers in PV cells. We have demonstrated the versatility of this approach by making PV cells using perovskite, organic semiconductor and colloidal quantum dot absorbing layers. For example, we showed that it is possible to reach more than 18% efficiency with carbon nanotube top electrodes in perovskite solar cells. Furthermore, we have found that non-conducting polymers wrap carbon nanotubes and can – contrary to common belief – produce very high quality electronic films (patent application pending). The exact mechanism for this is still under investigation, but opens the door to a whole range of science and applications as it allows e.g. the fabrication of a conductive substrate and/or barrier film.

This DPhil (PhD) project will build on these results and continue with the development of nanotube/polymer/graphene/titania/tin oxide combinations to produce the next generation of nanohybrid particles. It will aim at exploring the possibilities of using non-conjugated polymers to wrap carbon nanotubes for making conductive films and how to integrated graphene and carbon nanotube based electrodes into PV cells both as external contacting layers and as internal electrodes capable of implementing tandem cell designs for various PV technologies. In addition to spin-coating, we will explore the capabilities of a custom made spray-coater in the department which can deposit nanoparticles including carbon nanotubes, aiming to make this process compatible with roll-to-roll fabrication.

The three main objectives of this project are:
• Understand the wrapping of carbon nanotubes with non-conjugated polymers and explore its science and commercial potential.
• Make solar cells with nanotube/polymer/graphene/titania/tin oxide combinations to produce the next generation of nanohybrid particles for PV electrodes.
• Demonstrate spray coating of these electrodes compatible with roll-to-roll fabrication.

This project is supervised by Prof Robin Nicholas and Dr Moritz Riede in association with the EPSRC Centre for Doctoral Training Studentship in New and Sustainable Photovoltaics. A fully-funded Oxford-Radcliffe Studentship is available to an outstanding candidate who is accepted for this position. The studentship will offer 4 years’ full funding in partnership with the annual EPSRC CDT studentship funding competition, and as such is only open to EPSRC eligible (Home or EU) students. The candidate awarded this studentship will become a member of University College.

Entry requirements can be found on the Graduate Admissions Website.

Supervisor: Prof Robin Nicholas robin.nicholas@physics.ox.ac.uk +44 (0)1865 272250
Co-Supervisor: Dr Moritz Riede moritz.riede@physics.ox.ac.uk +44 (0)1865 272377

Prof Paolo Radaelli and Prof Andrea Cavalleri

Breaking symmetry with light: ultra-fast ferroelectricity and magnetism from non-linear phononics

A collaboration between Prof. Paolo G. Radaelli and Prof. Andrea Cavalleri, who holds a joint appointment between the Clarendon Laboratory and the Max Planck Institute for the Structure and Dynamics of Matter. (Hamburg).

Radaelli Cavalleri non linear graphic_0.png

Figure 1: schematic representation of non-linear photo-ferroicity. THz or far-IR ‘pump’ photons excite an IR-active mode (right), which is coherently coupled with a Raman mode (left). The rectified component of the Raman mode transiently generates ferromagnetism or ferroelectricity, which is probed coherently with a near-IR or visible light beam (top left).

The use of light to control the structural, electronic and magnetic properties of solids is emerging as one of the most exciting areas of condensed matter physics. One promising field of research, known as femto-magnetism, has developed from the early demonstration that magnetic ‘bits’ in certain materials can be ‘written’ at ultra-fast speeds with light in the visible or IR range [1]. More radically, it has been shown that fundamental materials properties such as superconductivity can be ‘switched on’ transiently under intense illumination [2]. Recently, the possibilities of manipulating materials by light have been greatly expanded by the demonstration of mode-selective optical control, whereby pumping a single infrared-active phonon mode results in a structural/electronic distortion along the coordinates of a second, anharmonically coupled Raman mode – a mechanism that was termed ‘nonlinear phononics’. Crucially, the Raman distortion is partially rectified, meaning that it oscillates around a different equilibrium position than in the absence of illumination. Very recently, it was realised that, under appropriate conditions, the rectified Raman distortion can transiently break the structural and/or magnetic symmetry of the crystal. Such symmetry breaking persist for a time corresponding to the carrier envelope of the pump, which can be less than a picosecond, and can give rise to the ultra-fast emergence of ferroic properties such as ferromagnetism and ferroelectricity. Through symmetry analysis and first-principle calculations, we have identified several promising ‘photo-ferroic’ materials that should display these effects, with potential applications in ultra-low-power information storage, ultra-fast electronics and many more.

This DPhil project will give the successful candidate the opportunity to pioneer this new field of research. Initial experiments on the candidate ‘photo-ferroic’ materials that we have already identified will be performed at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany. As a mode-selective pump, we will employ coherent laser radiation in the THz or far-IR range with sub-ps carrier envelopes, while the transient emergence of the ferroic properties will be probed with second-harmonic generation (SHG) and/or Faraday rotation of near-infra-red light. Later on in the project, changes in the crystal and magnetic structures of the materials will be probed with X-rays at free electron laser sources such as the European XFEL in Hamburg. Meanwhile, the candidate will develop search strategies for new classes of ‘photo-ferroic’ materials, based on symmetry and density functional theory calculations. He/she will develop the materials specifications in collaborations with crystal growers in Oxford and elsewhere, and will be involved hands on in all aspects of the design and realisation of the experiments and the data analysis.

The experimental part of this project will be predominantly based in Hamburg, so it is essential for the candidate to be willing and able to be based in Germany for extended periods during the DPhil.
[1]Femtomagnetism: Magnetism in step with light. Uwe Bovensiepen, Nature Physics 5, 461 - 463 (2009) abstract pdf
[2] See for example M. Mitrano,et al., ‘Possible light-induced superconductivity in K3C60 at high temperature’, Nature, 530, 461–464 (2016). [more at this link].
[3] Nonlinear phononics as an ultrafast route to lattice control, M. Först et. al., Nature Physics, 7, 854–856 (2011).

Supervisor: Prof Paolo Radaelli paolo.radaelli@physics.ox.ac.uk
Co-Supervisor: Prof Andrea Cavalleri andrea.cavalleri@physics.ox.ac.uk

Prof Paolo Radaelli and Dr Roger Johnson

Harnessing the power of topology in oxide electronics for future IT components

This project will be co-supervised by Prof. Paolo G. Radaelli and Dr Roger D. Johnson, who holds a Royal Society University Research Fellowship in the Clarendon Laboratory

antiferromagnetic.png

Figure 1. Map of the antiferromagnetic vortices in a-Fe2O3 layer. Colour represents the axis of the antiferromagnetic moments (colour bar bottom right). the two insets (left and right) highlight a vortex and anti-vortex respectively. The three colours (red, green, blue) represent the three possible spin directions allowed by the magnetic symmetry of Fe2O3.

In spite of its extraordinary success in fuelling the IT revolution, silicon (CMOS) technology is intrinsically not energy-efficient, because it relies on the movement of electrical charge, which is associated with Joule heating. One of the front runners among ‘beyond-CMOS’ technologies is spintronics, which relies on spins rather than charges to transfer and process information; however, much of the energy efficiency of spintronics is lost if spin flipping – the elementary spintronic operation – must in itself be performed by electrical currents. For this reason, voltage control of magnetic components is widely considered to be the key to large-scale commercialisation of spintronics [1-3]. The field of oxide electronics emerges precisely from the consideration that oxides, especially those containing magnetic transition metal ions such as Co, Mn and Fe, can display a multitude of intriguing electrically-controlled multi-functional properties in their insulating states, whilst integration with CMOS is already a reality. The potential of oxide electronics can be further enhanced by exploiting the power of topology, which involves, quite literally, tying spins into ‘magnetic knots’. In work recently published in Nature Materials [4], an international team of collaborators lead by Professor Paolo G. Radaelli (Oxford Physics) presented a major breakthrough in this field [5]: they created, for the first time, small-scale hybrid oxide/metal topological magnetic objects, consisting of tightly-coupled spin vortices in antiferromagnetic iron oxide (a-Fe2O3) and ferromagnetic metallic cobalt (Co). One particularly appealing feature of this system is that it employs cheap and readily available materials (a-Fe2O3 is the most abundant constituent of common rust!) and relatively simple fabrication, raising hopes that these systems could be deployed on a commercial scale in the future (for an extended lay description, see the Oxford Physics Newsletter – Autumn 2018).
This EPSRC-funded DPhil project will give the successful candidate the opportunity to develop this line of research in different directions, both fundamental and applied:
• Identify and grow new oxides with topological magnetic states, study their fundamental properties and image the topological structures at the nanoscale using state-of-the-art microscopy techniques.
• Experiment with novel ways to control topological magnetic states, exploiting either intrinsic magnetoelectric properties or interactions with active substrates
• Design and test prototype devices, built using electron beam lithography and other clean room processes.
This project is likely to involve a combination of experimental techniques, such as:
• Growth of thin films and devices – currently in collaboration with the groups of Prof. Thorsten Hesjedal (Oxford Physics), Prof. Chang-Beom Eom (Univ. of Wisconsin – Madison) and Prof. Venky Venkatesan (National University of Singapore).
• Advanced microscopy. We employ spectral microscopy (PEEM – we invented and continue to develop many of the relevant data analysis methods) at the Diamond synchrotron, Magnetic Force Microscopy (MFM) and the Magneto-Optical Kerr Effect to image multi-functional domains, which are the fundamental unit of information storage in oxides.
• Dielectric and transport measurements (in house)
• Elastic neutron scattering. We will perform experiments on bulk and films samples predominantly at the ISIS facility at Rutherford Appleton Laboratory.
• X-ray scattering, including resonant and non-resonant magnetic X-ray diffraction with hard and soft X-rays. We run state-of-the-art laboratory instrumentation in the Clarendon Laboratory, but we perform most of our high-end experiment at the Diamond Light source.
• Nanofabrication. In collaboration with National University of Singapore, we will be using electron beam lithography and other clean-room methods to design and build prototype oxide quantum materials devices.
Depending on the candidate's interests, the project may also include a computational element. In collaboration with the Materials Modelling Group in the Department of Materials (Prof. Feliciano Giustino), we employ Density Functional Theory methods and other computational techniques to model the functional properties of oxides and to predict their behaviour in different architectures. There will also be an opportunity of extended stays at one of the collaborating institutes to acquire new skills.

For more information email Prof. Paolo Radaelli and visit the group webpages.

[1] Matsukura, F., Tokura, Y. & Ohno, H. Control of magnetism by electric fields. Nature Nanotechnology 10, 209–220 (2015).
[2] Eerenstein, W., Mathur, N. D. & Scott, J. F. Multiferroic and magnetoelectric materials. Nature 442, 759–65 (2006).
[3] Ramesh, R. & Spaldin, N. A. Multiferroics: progress and prospects in thin films. Nature Materials 6, 21–9 (2007).
[4] F. Chmiel et al., Nature Materials 17, pages 581–585 (2018)
[5] M. Fiebig, Nature Materials 17, pages 567–568 (2018)

Supervisor: Prof Paolo Radaelli paolo.radaelli@physics.ox.ac.uk
Co-Supervisor: Dr Roger Johnson roger.johnson@physics.ox.ac.uk

Electrical control of magnetism in oxide films and devices

This project will be co-supervised by Prof. Paolo G. Radaelli and Dr Roger D. Johnson, who holds a Royal Society University Research Fellowship in the Clarendon Laboratory

Radaelli  Johnston - oxide films graphic.jpg

Figure 1. a: a BiFeO3 epitaxial films with patterned electrical contacts, which was measured at ISIS and Diamond. b: image of a small area of the film, obtained using vector-mapped x-ray magnetic linear dichroism photoemission electron microscopy (XMLD-PEEM). c: Domains in an Fe2O3 thin film. Different colours represent different antiferromagnetic domains

One of the most promising routes towards a new generation of fast, low-power electronics is the electrical control of magnetism in insulators[1-3]. This approach exploits the ability to switch the antiferromagnetic state in several classes of oxides by applying a small "writing" voltage. The spin polarisation can then be transferred to a ferromagnetic material through an interface, and then 'read' in a conventional way, e.g., using a Tunnelling MagnetoResistance junction as in hard-disk reading heads. This scheme could be employed to produce fast and efficient non-volatile memories, with no 'writing' current to produce Joule heating and therefore dissipate energy.

We have recently developed a suite of techniques for simultaneous imaging of antiferromagnetic/ferromagnetic domains and their electrical switching in epitaxial oxide films and devices. We use a combination of synchrotron X-ray diffraction and microscopy, in-house Magnetic Force Microscopy (MFM) and neutron diffraction, which give us access to domains over length scales from 1 cm to < 100 nm. In the past two years, we obtained some very exciting results on thin films and devices of BiFeO3, grown by our collaborators at the University of Madison (Fig. 1)[4-6]. In very recent experiments, we directly imagined the process of electrical switching in BiFeO3 and demonstrated the coupling of the BiFeO3 domains with the ferromagnetic domains of a thin metal over-layer. Even more recently, we demonstrated similar effects in epitaxial films of Fe2O3, grown by one of our students in our lab (see Figure 1c). The domains in Fe2O3 display topological structures similar to nematic liquid crystals.

This EPSRC-funded DPhil project will give the successful candidate the opportunity to develop this line of research in different directions:

• Identify and grow new materials with electrically controllable domains
• Experiment with novel ways to switch the magnetic state of the domains, e.g., through the piezoelectric effect
• Build and test prototype devices using electron beam lithography and other clean room processes.

This project is likely to involve a combination of experimental techniques, such as:

• Elastic neutron scattering. We will perform experiments on bulk and films samples predominantly at the ISIS facility at Rutherford Appleton Laboratory.
• X-ray scattering, including resonant and non-resonant magnetic X-ray diffraction with hard and soft X-rays. We run state-of-the-art laboratory instrumentation in the Clarendon Laboratory, but we perform most of our high-end experiment at the Diamond Light source.
• Dielectric and transport measurements. One of our specialities is to perform measurements of ferroelectricity in extremely high magnetic fields (up to 65 T – a record in the UK), using the pulsed-magnetic-field facility in the Clarendon Laboratory, but a complete set of more standard measurements is also available.
• Advanced microscopy. We employ spectral microscopy (PEEM) at Diamond, Magnetic Force Microscopy (MFM) and the Magneto-Optical Kerr Effect to image multi-functional domains, which are the fundamental unit of information storage in oxides.
• Nanofabrication. We will be using electron beam lithography and other clean-room methods to design and build prototype oxide quantum materials devices.

Depending on the candidate's interests, the project may also include a computational element. In collaboration with the Materials Modelling Group in the Department of Materials, we employ Density Functional Theory methods and other computational techniques to model the functional properties of oxides and to predict their behaviour in different architectures.

For more information email Prof. Paolo Radaelli and visit the group webpages.

[1] Matsukura, F., Tokura, Y. & Ohno, H. Control of magnetism by electric fields. Nature Nanotechnology 10, 209–220 (2015).
[2] Eerenstein, W., Mathur, N. D. & Scott, J. F. Multiferroic and magnetoelectric materials. Nature 442, 759–65 (2006).
[3] Ramesh, R. & Spaldin, N. A. Multiferroics: progress and prospects in thin films. Nature materials 6, 21–9 (2007).
[4] Coherent magneto-elastic domains in multiferroic BiFeO3 filmsN. Waterfield Price, R. D. Johnson, W. Saenrang, F. Maccherozzi, S. S. Dhesi, A. Bombardi, F. P. Chmiel, C.-B. Eom, P. G. Radaelli Phys. Rev. Lett. 117, 177601 (2016).,
[5] Electrical Switching of Magnetic Polarity in a Multiferroic BiFeO3 Device at Room Temperature, N.W. Price, R.D. Johnson, W. Saenrang, A. Bombardi, F.P. Chmiel, C.B Eom, and P.G. Radaelli, Phys. Rev. Appl. 8, 014033 (2017).
[6] Deterministic and robust room-temperature exchange coupling in monodomain multiferroic BiFeO3 heterostructures, W. Saenrang, B.A. Davidson, F. Maccherozzi, J.P. Podkaminer, J. Irwin, R.D. Johnson, J.W. Freeland, J. Íñiguez, J.L. Schad, K. Reierson, J.C. Frederick, C.A.F. Vaz, L. Howald, T.H. Kim, S. Ryu, M.v. Veenendaal, P.G. Radaelli, S.S. Dhesi, M.S. Rzchowski & C.B. Eom, Nature Comm., 8, 1583 (2017).

Supervisor: Prof Paolo Radaelli paolo.radaelli@physics.ox.ac.uk
Co-Supervisor: Dr Roger Johnson roger.johnson@physics.ox.ac.uk

Dr Moritz Riede and Profs Chris Nicklin

Domain evolution in vacuum processed bulk heterojunction organic solar cells

The solar cells at the centre of this research project have the potential to allow us to harness the power of the sun clean and at cost lower than coal everywhere we are and go, even in the UK. They can be made for example light like cardboard, flexible such they can be rolled up like a newspaper, and they could become much cheaper than existing solar cell technologies. To achieve this, our solar cells are not based on silicon, the material of most solar cells currently sold, but on organic semiconductors, and they are close to commercialisation.
The electrical and optical properties of organic solar cells (OSC) depend on the molecular arrangement of the organic semiconductors and the domains they form in the thin organic layers used to absorb the light (~10-100nm). This initial microstructure of the thin film forms during the deposition process and can evolve during the operation of the OSC.

The goal of this project is to work with and expand the capabilities of a vacuum deposition system we have recently installed at Diamond (see DOI: 10.1063/1.4989761) and use it to investigate the microstructure formation and evolution in-situ using grazing incidence wide and small angle X-ray scattering (GIWAXS and GISAXS). Getting and maintaining a favourable microstructure is crucial for for many processes in OSCs, from efficient light absorption to fast transport of these charge carriers to their respective electrode. Thus, we expect that the results will improve our understanding of the OSC device physics and lead to improved device performance, which will be critical on the route towards commercialisation.

The work will be carried out in a well established collaboration between Diamond and Oxford University, brining together expertise in microstructural characterisation of this organic films, device fabrication and OSC device physics.

Supervisors: Moritz Riede and Chris Nicklin

Email Dr Moritz Riede at moritz.riede@physics.ox.ac.uk.

Dr Moritz Riede

Understanding the Fundamental Efficiency Limits of Organic Solar Cells

The first wave of products using organic semiconductors has very successfully entered the market: organic light emitting diodes (OLED) are used in the displays of many mobile phones and TVs, featuring brilliant colours etc.. Key to their commercial success are vacuum processing of small organic molecules under precise control into well-defined multilayer stacks and the use of molecular doping, i.e. the modification of a semiconductor's properties by a controlled addition of "impurities". Both concepts are much less used in organic solar cells (OSC), but it can be applied here with similar benefits, enabling a cheap, efficient, light-weight and flexible renewable energy source. Best proof of this is that the current technology leader, the start-up Heliatek, is using both concepts.
Record OSC have achieved power conversion efficiencies (PCEs) of ~11-12%. However, this value is still low compared to those of commercial rigid and monochrome inorganic competitors (~20%) and the values for OSC have remained nearly the same since 2013, hindering a fast large scale commercial breakthrough. The main reasons for this are high energy losses at the open circuit voltage, of which much remains unclear. The goal of this DPhil is to get experimental access to the exact location in the OSC, i.e. the donor-acceptor interface, where these losses take place, characterise them and subsequently find ways to modify and control these processes. Only then will it be possible to significantly reduce these losses and to demonstrate PCEs exceeding 15% for OSC.
For the preparation of the samples we rely on vacuum processes, similar to those that are used for the production of OLEDs. To arrive at a better understanding of the loss processes, an extensive range of experimental methods to characterise the optical and electronic behaviour of our samples will be used. In this research, we will be collaborating with other groups in Oxford and with international experts from e.g. Canada, Germany and Switzerland.

Email Dr Moritz Riede at moritz.riede@physics.ox.ac.uk.

Dr Nicole Robb

Development of viral biosensors

Many viruses (from the influenza virus to the Zika virus) can cause debilitating and deadly diseases, and their sensitive, specific and rapid detection is a major challenge in their identification and control. We have been developing novel detection methods (in part due to previous successful MPhys projects) based on single-molecule fluorescence imaging, single-particle detection and machine learning, to detect the influenza virus on a compact microscope that can be used in clinical settings; the detection can be completed in just a few minutes, as opposed to existing assays that require many hours.

This project will extend the previous biosensing work in many possible ways: optimizing detection by investigating different methods of virus labelling, improving the particle illumination scheme, use of different DNA/RNA/protein sensors to add specificity and adapt the assay to clinical settings, and developing new data analysis methods to increase the throughput of the assays.

Supervisor: Dr Nicole Robb nicole.robb@physics.ox.ac.uk +44 (0)1865 272357

Prof Henry Snaith

Perovskite Solar Cells


(Lee et al. Science 2012)

In the last 12 months we have had an unexpected breakthrough in the field
of emerging photovoltaics with the realization of over 15% efficient solid-state hybrid solar
cells based on organometal halide perovskite absorbers. These solar cells are fabricated from extremely inexpensive material and are remarkably efficient, with prospects for significant improvement in the next few years, setting them apart from other emerging PV technologies. We have DPhil projects centred around perovskite solar cells, with activity ranging from synthesising new perovskite absorbers, with a goal to understand the influence of structure and composition upon charge generation and electron-hole lifetime, through to thin film processing, device fabrication and advanced spectroscopy.

Email Prof Henry Snaith at h.snaith@physics.ox.ac.uk

Prof Snaith has a further project, which is a joint project with Prof Laura Herz. Please see entry above for 'Prof Laura Herz & Prof Henry Snaith'.

Prof Robert Taylor

Electrically-driven single photon sources in non-polar nitrides

This project involves the use of photon counting microphotoluminescence spectroscopy to investigate the optical properties of InGaN quantum dots grown and patterned into electrically driven single photon sources. The student will be involved in cryogenic experiments using pulsed and CW lasers and pulsed high-frequency electrical sources. The Taylor group has extensive experience in optical spectroscopy of semiconductor materials and the student would join a vibrant group which has an excellent track record of publication in high-impact journals.

A quantum light source is a device which generates either individual photons or pairs of photons in a regulated streami. Such devices are a key enabling technology for future quantum systems, enabling secure communication networks, new paradigms of computation and new metrological techniques. The project will seek to move away from impractical systems which require either large external pump lasers or cryogenic cooling (or both), towards compact voltage-driven devices, operational at room temperature or using only on-chip Peltier cooling. Moreover, if the source can provide deterministically polarised photons, this enhances the efficiency of quantum key distribution (QKD) systemsii. The figure below shows some promising recent results which underpin the work of this project.

Full details of Prof. Taylor’s research and publications can be found here.
Email Prof. Robert A. Taylor at: r.taylor1@physics.ox.ac.uk

Taylor, R graphic_0.jpg

i Shields, A.J. Nat. Photon. 2007, 1, 215.
ii P. Bhattacharya Semicond. Sci. Technol. 2011 26 014002.

Prof Stephen Tucker

Ion Channels and Nanopores: From Structure to Function

Almost every single process in the human body is controlled at some level by electrical signals, from the way our hearts beat, the way our muscles move, to the way we think. These electrical signals are generated and controlled by a family of proteins called 'ion channels' which reside in the membrane of every living cell and which act as 'electrical switches' to control the selective movement of charged ions like potassium (K+) and Sodium (Na+) into and out of the cell.

Work in our lab uses a range of multidisciplinary approaches (molecular biology, electrophysiology, single-molecule fluorescence, molecular dynamics and crystallography) to study the structure and function of these channels. We have a range of projects available to people with physics, engineering, computing, biochemistry and physiology backgrounds.

In particular, we currently have an exciting new PhD project available to investigate how the unusual behaviour of water within the nano-sized pore of an ion channel influences its behaviour. This project would suit someone with a computational background and/or programming skills as it involves development of a new software tool to annotate membrane protein structures.

In collaboration with other colleagues in Oxford, we also have PhD projects available to work on the structural determination of ion channel drug binding sites using serial femtosecond crystallography and X-ray free electron laser (XFEL).

For further details, contact Prof Stephen Tucker at stephen.tucker@physics.ox.ac.uk or visit https://biophysics.physics.ox.ac.uk/tucker/

Prof Andrew Turberfield

DNA Nanostructures

DNA Walker.png

Our research focuses on the creation of functional nanosystems using biomometic strategies for self-assembly programmed by sequence design of biomolecular components. Synthetic DNA components can be designed, through control of their base sequences, to assemble into molecular structures and machines with nanometre precision. DNA devices can be active: DNA hybridization is a source of energy that can be used to power molecular devices and an important part of the group's activity is devoted to making synthetic molecular motors with the aim of applying them to more advanced strategies for molecular construction (including chemical synthesis) modelled on the molecular machinery of the cell. Self-assembly, and the interactions of molecular devices, can also be exploited to perform molecular computation. Applications range from physics and computer science to structural biology and medicine.
Projects will include both design and experiment. Tools available include single-molecule optical techniques (including super-resolution microscopy), atomic force microscopy, transmission electron microscopy, fluorimetry, spectrophotometry and biochemical techniques such as gel electrophoresis. Possible projects include:

1) Templated assembly of molecular electronic and photonic devices, using DNA nanostructures as breadboards to assemble molecular components (with Arzhang Ardavan, Oxford);

2) Molecular machinery capable of sequence-controlled polymer synthesis programmed by a synthetic gene (an "artificial ribosome"), including systems for combinatorial selection of functional oligomers with potential applications in drug discovery (with Rachel O’Reilly, Birmingham);

3) Design and study of the folding pathways of DNA nanostructures, including the use of selection and evolution experiments to discover and refine design strategies;

4) Hybrid peptide – nucleic acid nanostructures, exploiting the ability of DNA templates to augment and control the chemical functionality of peptide assemblies (with Dek Woolfson, Bristol);

5) DNA structures and devices designed to operate within cells as tools for biological research and platforms for nanomedicine.

6) Molecular computation, creating control mechanisms for molecular robotic devices (with Luca Cardelli, Computer Science)

More ...

Email Prof Andrew Turberfield at: andrew.turberfield@physics.ox.ac.uk

Condensed Matter Physics is also associated with the following DPhil programmes:

DPhil Systems Approaches in Biomedical Sciences (EPSRC & MRC CDT)
DPhil Systems Biology (EPSRC CDT)
DPhil New and Sustainable Photovoltaics (EPSRC CDT)
DPhil Science and Application of Plastic Electronics (EPSRC CDT)
DPhil Synthetic Biology (EPSRC & BBSRC CDT)

If you are interested in the DPhil New and Sustainable Photovoltaics (EPSRC CDT), you can find more detailed information under the respective projects above and here.
And if you are interested in the DPhil Science and Application of Plastic Electronics (EPSRC CDT), you can find more detailed information under the respective projects above and here.