School of Physics & Astronomy

Find a PhD Project Here

Opportunities for fully funded PhD or EngDoc research projects are available in all fields of research within the School. You may search for current projects on this page. APPLY HERE for a PhD Place.

 PhD in Photonics
 PhD in Condensed Matter
 PhD in Astrophysics

Search current PhD opportunities in the School of Physics & Astronomy:-




Astrophysics

3D atmosphere simulations of giant gas planets and brown dwarfs
Helling, Dr Christiane - ch80@st-andrews.ac.uk

This project qualifies as an STFC studentship in Data-Intensive Science.

Extrasolar planets have proven to be far more diverse than the planets in the solar system. This project will deal with modelling globally circulating atmospheres to study cloud formation and lightning in extrasolar planets.

Cloud formation is a major challenge for understanding planetary atmospheres because clouds determine the spectral appearance of the planet (and also of brown dwarfs) and they influence the dynamic behaviour of the atmosphere. 3D simulations will be used which provide a rich data set for the atmosphere structure as well as for the details of cloud and gas-chemistry. Beside the scientific analysis of the modelling data, the project requires 3D visualisation for data analysis purposes.
A bad case of split personality
Jardine, Prof Moira - mmj@st-andrews.ac.uk

Recent studies of the magnetic fields of very low mass stars shows a strange and so far unexplained behaviour. Some have strong, simple magnetic fields, and some have much weaker, complex, solar-like field magnetic fields. We do not fully understand why this difference occurs, but this project involves using the maps of the magnetic fields of these star to explore the physics of their coronae and winds and to examine the impact on any orbiting planets.
A scalable approach to modelling gravitational microlensing events for exoplanet demographics in the WFIRST era
Dominik, Dr Martin - md35@st-andrews.ac.uk

-> This project qualifies as an STFC studentship in Data-Intensive Science. <-

Determining the demographics of cool planets by means of microlensing is one of the key science goals of NASA’s WFIRST (Wide Field Infrared Space Telescope) mission. However, current approaches for modelling the acquired data are already unsuitable for managing the much smaller number of gravitational microlensing events that are currently detected by the most advanced ground-based surveys. The major bottleneck to be overcome is the reliance on human judgement in the data analysis process. Any scalable solution needs to be fully-automated (“data-in-model-out”), taking into account accurately the statistics of the photometric data (i.e. not claiming planets from statistical “noise”) and exploring highly-dimensional non-linear parameter space.
Angular momentum loss and mass loading of stellar winds - slingshot prominences in action
Jardine, Prof Moira - mmj@st-andrews.ac.uk

Many solar-like stars show cool, dense clouds of gas trapped within the million-degree plasma of their outer atmospheres (or coronae). These so-called ``slingshot prominences'' carry away angular momentum when they are ejected and also are also responsible for mass-loading of the stellar wind. As a result, they may form an important part of the spin-down of young stars, and their impact on orbiting planets may lead to enhanced stripping of the planetary atmosphere.
Annihilation of Dark Matter
Zhao, Dr Hongsheng - hz4@st-andrews.ac.uk

A main diagnostic of the particle dark matter is its annihilation rate, which depends sensitively on the dark matter density profile. The student will explore various density models of the dark matter, taking into account the effects of black holes and baryonic dynamics.
Brown dwarfs and rogue planets in star forming regions
Scholz, Dr Aleks - as110@st-andrews.ac.uk

What is the lowest mass object that can form like a star? And how many massive planets are ejected from their planetary systems during the formation process? These two questions will be tackled in this project.

Over the last years, we have carried out a search for the lowest mass free-floating objects in star forming regions, in a project called SONYC (short for Substellar Objects in Nearby Young Clusters). In SONYC we used the largest existing ground-based telescopes to make ultradeep surveys of the youngest clusters on the sky. While we found plenty of brown dwarfs (with some interesting evidence for environmental difference in the formation of brown dwarfs), we did not find many objects with super-Jupiter masses, the presumed ejected giant planets. If they exist (and we expect that they do), they will be below our mass threshold of 5 Jupiter masses and are still to be discovered.

In the next step of this project (and in this PhD project) we will use the James Webb Space Telescope to explore the domain of free-floating rogue planets with masses between 1 and 5 Jupiter masses. We have good chances to get observing time to get this project started right after the JWST begins operation in 2018. The student will prepare the observations and explore follow-up avenues, with JWST and other facilities, and then be the first to analyse the data. In addition, we will work with the second data release from Gaia to pin down the fundamental parameters of young brown dwarfs. This will lead to new contraints on star formation simulations and insights into the transition from star to planet formation.

This will be a strongly observational project, which requires to learn the details of optical and infrared observations, the physics of ultracool objects, the intricacies of disentangling emission from objects, disks, and accretion, as well as an interest in collaborating with people from the theory side, including atmospheric physics and star/planet formation.
Data-intensive Science: Wide-angle search for extrasolar planets
Cameron, Prof Andrew - acc4@st-andrews.ac.uk

The University of St Andrews is a founding institutional member of the Wide-Angle Search for Planets (WASP) project, which is a consortium comprising 6 UK universities and 3 overseas observatories. We use two arrays of wide-field camera lenses backed by large-format CCDs to perform high-precision photometry of millions of stars each night, looking for the 1% dips in light that betray gas-giant planets whose orbital planes are close enough to the line of sight that they transit their host stars. With over 166 hot Jupiters confirmed to date by radial-velocity follow-up, WASP is the world’s leading ground-based producer of transiting planets.

Over the last decade, WASP has amassed a database of light curves on some 31 million objects. In the era of NASA’s TESS mission, the WASP data archive will have an important role to play in documenting the past variability history of new planetary systems and variable stars identified from space.

The WASP database has the potential to address many other areas of time-domain astrophysics. We are already applying supervised and unsupervised machine learning methods to distinguish objects of astrophysical interest from false alarms caused by systematics, and to classify objects showing astrophysical variability. This allows likely transiting planets to be distinguished from eclipsing binary stars, rotational variables and pulsating stars. Early validation by rejection of such “astrophysical false positives” increases greatly the efficiency of radial-velocity follow-up. This work also involves cross-matching with other large astronomical databases: 2MASS for infrared colours and angular-diameter estimates, and Gaia for parallaxes and proper motions.

Students working on this Data-Intensive Science project will acquire training and experience in a variety of machine classification techniques, Bayesian parameter estimation with Gaussian-process regression to model systematics and correlated noise, Gaussian mixture models and hierarchical Bayesian inference for extracting population parameters.

Determining the origins of galaxy bimodality using hierarchical Bayes methods
Tojeiro, Dr Rita - rmftr@st-andrews.ac.uk
Wild, Dr Vivienne - vw8@st-andrews.ac.uk

->This project qualifies as an STFC studentship in Data-Intensive Science.<-

How galaxies form and evolve is one of the outstanding questions of modern astrophysics. Extremely large spectroscopic surveys are providing an increasingly detailed census of both local and distant galaxies. Considerable progress is being made on quantifying the changing demographics of the galaxy population over the majority of the age of the Universe, but significant improvements in methods are demanded by the increasingly large samples, and often decreasing quality of the individual observations.

In the last decade a Bayesian approach to the fitting of sophisticated models to high quality spectra and/or multiwavelength photometry has become common place in the analysis of galaxy spectral energy distributions (SEDs) at all redshifts (Walcher et al. 2011). The result are robust physical properties, such as stellar mass and star formation history, as well as well understood degeneracies between fitted parameters. We now know that massive galaxies come in two main types - elliptical/quiescent and spiral/star-forming. Understanding why this is, is a key science goal in astrophysics.

How much information are we missing by treating galaxies as independent entities to determine their physical properties, rather than a population of objects with common origin? How can we use the same fitting approaches for lower quality observations of increasingly large samples?

Hierarchical Bayes techniques have appeared in the astronomical literature to solve problems as diverse as QSO redshift estimation (Bovy et al. 2011), exo-planet orbit analysis (Hogg et al. 2011), properties of SN 1a light curves (Mandel et al. 2009), and photometric redshifts (Leistedt et al. 2016). They differ from standard Bayesian methods by fitting the entire dataset in a coherent manner, instead of single objects as entirely independent entities. By applying these methods to galaxy evolution studies, we will improve our ability to break degeneracies. These methods could be applied to e.g. complete populations of galaxies in spectroscopic or photometric surveys, or entire integral field datacubes of single galaxies.

The school of physics and astronomy at the University of St Andrews is a member of the UK participation group in SDSS-IV (fourth generation of Sloan Digital Sky Surveys, www.sdss.org), a large international collaboration encompassing several astronomical surveys (including MaNGA and eBOSS). Drs Wild, Weijmans, and Tojeiro all have data access. Note that access to data from the SDSS-IV survey is rare in the UK, and guaranteed through the supervisors core involvement in the survey.

The project involves the development of statistical techniques to make them applicable to astronomical datasets. Applications from students with a background in maths, statistics or physics and interest in astrophysics are welcome, as well as from students with a background in astrophysics but strong aptitude for maths and statistics.

Please contact Vivienne Wild. the lead supervisor for the project, for more information (vw8@st-andrews.ac.uk)

References:
Bovy J., Myers A. D., Hennawi J. F. et al. arXiv:1105.3975
Hogg D. W., Myers A. D., Bovy J., 2010, ApJ, 725, 2166
Leistedt B., Mortlock D., Peiris H., 2016, MNRAS, 460, 4258
Mandel K. S.; Wood-Vasey W. M., Friedman A. S., Kirshner R. P., 2009, ApJ, 704, 629
Walcher C. J., Groves B., Budavri T., Dale D., Ap&SS, 2011, 331, 1
Diffuse ionized gas in galaxies
Wood, Dr Kenny - kw25@st-andrews.ac.uk

Extensive layers of diffuse ionized gas are observed in the Milky Way and other galaxies. This project will study the structure, ionization, heating, and dynamics of diffuse ionized gas using a combination of 3D Monte Carlo radiation transfer codes and recent 3D dynamical models of a supernova driven ISM.
Echo Mapping of Black Hole Accretion Flows in Active Galactic Nuclei
Horne, Prof Keith - kdh1@st-andrews.ac.uk

This project qualifies as an STFC studentship in Data-Intensive Science.

Light travel time delays enable micro-arcsecond mapping of accretion discs and broad emission-line regions around the super-massive black holes in the nuclei of active galaxies. Using our share of time on the LCOGT robotic telescope network, along with data from HST, Swift and Kepler satellites, we are monitoring spectral variations of Active Galactic Nuclei to measure black hole masses, accretion rates, and luminosity distances. By decoding information in the reverberating emission-line profiles, we make 2-dimensional velocity-delay maps of broad emission-line regions, mapping the velocity field and ionisation structure of the accretion flows. The student will acquire and analyse such datasets, fitting parameterised models using MCMC methods, image reconstruction using Horne maximum entropy fitting code MEMEcho, and photo-ionisation codes such as Ferland's Cloudy.
Feedback in young stellar clusters
Cyganowski, Dr Claudia - cc243@st-andrews.ac.uk

Most stars form in clusters, where energetic feedback from massive
(proto)stars--including outflows, ionization, heating, and
winds--shapes the environment and impacts accretion. The relative
importance of different feedback processes is a key outstanding
issue in our understanding of massive star formation.

The aim of this project is to conduct the first large-scale
observational study of the role and physics of feedback in massive
(proto)clusters. This will involve analyzing high-resolution data
from recently-upgraded (sub)mm and cm-wavelength interferometers, in
particular the Submillimeter Array (SMA), the Jansky Very Large Array
(VLA), and, potentially, the Atacama Large Millimeter/sub-millimeter
Array (ALMA). The observational results will be compared with
simulated observations of numerical models of massive star and
cluster formation.
Frictional charging of dust grains: lightning in discs?
Woitke, Dr Peter - pw31@st-andrews.ac.uk

Dust grains in protoplanetary discs generally charge up due to photo-effect, electron attachment, and charge exchange reactions with molecular ions. Grain-grain collisions can possibly lead to an additional statistical charging (contact electrification), which has not yet been thoroughly discussed in the disc community yet (see e.g. Muranushi 2010). If grains of different sizes collide, charge up size-dependently, and move selectively (by gravitational settling), a large-scale charge separation could build up, leading to lightning in discs. This scenario has been proposed to explain intra-cloud lightning observed in volcano plumes, as well as lightning in the Earth’s atmosphere and in exo-planets (Helling et al. 2016). Similar effects could take place in protoplanetary discs, causing radio emission and having a long-term impact of the chemical composition of the gas.

* Is frictional charging a key process for midplane ionisation and the MRI in discs?
* Can the gravitational settling of charged grains build up electrostatic fields in discs?
* Can this field overcome the break-down field to cause spontaneous discharge processes (lightning)?
* Where exactly, in the disc, are these processes most likely to occur?
* Could lightning lead to observable signals, like short-term radio variability?
* Could lightning have a long-lasting impact on the chemistry in the planet-forming region?

PhD-student is expected to implement triboelectric charging rates into ProDiMo, using typical turbulent dust velocities from MHD disc models. The resulting charge distribution of the grains will be studied depending on size and location in the disc, and consequences for large-scale electrification and lightning in discs shall be discussed.
GravityCam lucky-imaging microlensing survey
Dominik, Dr Martin - md35@st-andrews.ac.uk

GravityCam is a proposed mosaic camera composed of ~100 EMCCDs with a novel design that for the first time combines a wide field with a very fast readout, thereby achieving an angular resolution of 0.15’’ by means of lucky imaging and opening up an entirely new observing paradigm for ground-based astronomy, its only real competition being in space. A core science driver for GravityCam is a Galactic bulge microlensing survey that could go about 4 magnitudes deeper than current efforts for the same signal-to-noise ratio and exposure time, and thereby at the same sensitivity probe cool planets (or satellites) that are 100 times less massive, which gives access to a hitherto uncharted region in planet parameter space extending down to Lunar mass. In addition, as a unique and versatile instrument, GravityCam will be suitable for addressing a wide variety of scientific applications, including in particular studies of dark matter (by means of weak lensing), fast-varying astronomical objects, asteroseismology, variability and astrometry in crowded fields, occultations by small Solar-System bodies, and transiting extra-solar planets, while providing an extensive resource for general data mining of the high-speed variable sky.

You will have the opportunity to optimise the design of a GravityCam microlensing campaign by means of simulations in order to maximise the science output relating to the arising planet population statistics, which requires carefully balanced choices of exposure time and cadence dictating the total survey area. Moreover, you can take part in current observational efforts (MiNDSTEp and Robonet-II), pioneering crowded-field lucky-imaging photometry and real-time scheduling of microlensing targets across telescope networks.
Heating and Cooling in Hydro-Simulations of Protoplanetary Discs
Woitke, Dr Peter - pw31@st-andrews.ac.uk

New spatially resolved observations of protoplanetary discs have revealed so far unseen spatial structures within the discs, such as rings, holes, spiral arms, warps, shadows, and large vortices. They are detected at various wavelengths, in the gas and dust, in scattered light and in thermal emission. These structures are very likely direct signposts of the planet formation process in the discs, yet current hydrodynamical disc models suffer from a very basic uncertainty, namely the poor treatment of radiative transfer and heating/cooling effects in hydrodynamical disc models. The supervisor is an expert in the fields of chemistry, heating & cooling and radiative transfer, but these techniques need to be extended and merged with (magneto) hydrodynamics in 3D to get ready for the new challenges in the era of spatially resolved disc observations.

This project aims at merging current state-of-the-art modelling techniques concerning (magneto) hydrodynamics, chemistry and radiative transfer in protoplanetary discs. Based on the radiation thermo-chemical disc code "ProDiMo" which includes a very detailed treatment of 2D continuum and line radiative transfer, and gas energy balance, we aim at the production of numerical look-up-tables of equilibrium gas and dust temperatures, chemical and ice composition of the gas, and effective heating & cooling rates suitable for hydrodynamical disc simulations.

The task is to build a brigde between thermo-chemical and hydrodynamical disc simulations. The student will study and learn how to run both types of models, calculate the look-up-tables with ProDiMo, and then apply these in hydrodynamical disc simulations.
Mass Distribution of the Galaxy
Zhao, Dr Hongsheng - hz4@st-andrews.ac.uk

The mass distribution of the Galaxy is being / will be mapped out in great detail in the next decade with the numerous surveys of the Galaxy, including Segue, RAVE, GAIA, and completed ones like 2MASS, DENIS. A model for the potential and phase space of the galaxy is essential to bring various pieces of information together. The student will develop such models building on experience from existing models.
Optimal real-time scheduling for observations of transients across global telescope networks
Dominik, Dr Martin - md35@st-andrews.ac.uk

-> This project qualifies as an STFC studentship in Data-Intensive Science. <-

World-spanning networks of robotic telescopes have opened up new opportunities for the regime of time-domain astronomy. The deployment of such networks comes along with the roll-out of a new generation of powerful surveys that provide “transient factories”, calling for prompt and extensive follow-up monitoring. How can such resources be used efficiently and how can observations be coordinated? While the scheduling of telescopes so far has mostly been discussed from the perspective of service providers, we need to look at this from the perspective of the community of users who want to achieve a scientific objective using a diversity of resources coming from different providers. The selection of a specific target to be observed at a specific time by a specific instrument needs to take into account: 1) the science goals, 2) the acquired data on all potentially relevant targets, 3) the technical specifications of the instrument, 4) the observability of the targets. In particular, target priorities will change as fast as the targets vary themselves and data therefore need to be analysed in quasi-real time in order not to miss critical features. Consequently, a large amount of data need to be pulled together and processed immediately, while continuous monitoring requires uninterrupted operatability. Within larger user communities, objective functions and resulting monitoring strategies also need to consider the ownership of data and both individual and collective benefits. The University of St Andrews has pioneered the implementation of automated target selection strategies for the follow-up of ongoing gravitational microlensing events with the LCOGT/SUPAscope and MiNDSTEp networks. Students will face a technology challenge on data processing, modelling, and management at the intersection of astronomy and computer science, matching the requirement to achieve a fast throughput. Solutions to this sort of problem will likely to be transferable to serve applications in other areas.
Spins, spots and speculations: Rotation and activity at the star-planet transition
Scholz, Dr Aleks - as110@st-andrews.ac.uk

Rotation is a fundamental property of stars. The angular momentum regulation of stars is linked with the evolution of disks, the physics of magnetically driven winds, and the interior structure. Stars like the Sun start with a period of a few days, but spin down to periods of weeks and months over the course of billions of years. This project is focused on investigating the spindown of very low mass stars, the most abundant type of stars in our Galaxy, which present a serious challenge for our current understanding of stellar rotation. In contrast to solar-mass stars, they have long spindown timescales of ~1 gigayear or more. The extreme case are brown dwarfs, which do not seem to spin down over a Hubble time, comparable to giant planets. All this is probably related to the atmospheric physics, particularly the magnetic properties. We are therefore particularly interested in probing the link between rotation and magnetic activity. We have been granted observing time with the Kepler-2 mission to get lightcurves for very low mass stars and brown dwarfs are various stages of their evolution. Since these stars are magnetically very active, star spots cause a periodic modulation of the flux from which the rotation period can be measured with high accuracy. The same lightcurves also give information about magnetic spots. The archive of the Super-WASP planet search will also be used to study the longest timescales. Another dataset from the Very Large Telescope will be used to examine rotation rates in young free-floating planetary mass objects. There is scope for new observations carried out with large telescopes. We will measure rotation periods, probe the period-activity correlation, compare with new models for the stellar spindown, and investigate the possibility of gyrochronology (i.e. estimating ages from rotation rates) for red and brown dwarfs.
Star formation in dwarf galaxies
Bonnell, Prof Ian - iab1@st-andrews.ac.uk

This project is to develop the first models of resolved star formation on galactic scales. This will involve modelling a full galactic potential and how it drives the formation of molecular clouds and the onset of gravitational collapse and star formation. feedback from ionisation and supernova will be included to assess molecular cloud lifetimes and star formation efficiencies.
Star-Planet Interaction
Jardine, Prof Moira - mmj@st-andrews.ac.uk

Tau Boo is the only star for which we have been able to track the full cyclic reversal of the stellar magnetic field. This system is also well-known, however, because it hosts a Hot Jupiter that is so close to the star that it may lie within the stellar corona. What is the nature of the interaction between the star and planet in this case and is it related to the puzzling nature of the very short magnetic cycle? This project will investigate tau Boo and other similar star-planet systems.
The evolution of newborn Sun-like stars
Gregory, Dr Scott - sg64@st-andrews.ac.uk

When a newborn solar-like star emerges from its natal cloud it is still surrounded by a substantial disk of dust and gas. At this stage of pre-main sequence evolution the star interacts with the inner disk via its large-scale magnetic field, which channels gas onto the stellar surface at high velocity. Recent large observing programs have begun to reveal how their magnetic geometries are linked to their location in the Hertzsprung-Russell diagram. Tentatively, it appears as though solar-like stars are born with simple axisymmetric magnetic fields that become more multipolar/complex and non-axisymmetric as the stellar interior structure varies from fully to partially convective. Should this stellar structure change occur before the disk has dispersed it will have implications for the magnetic star-disk interaction, the coronal evolution of the star itself, the balance of torques in the star-disk system, and the rotation rate of the star. Using the latest observational data as a basis, the student will model the star-disk interaction and coronal magnetic evolution as stars evolve across the pre-main sequence.

For more evolved pre-main sequence stars, where the disk has dispersed but the star is still contracting under gravity, it has been observed that the scatter in X-ray luminosities decreases for stars in older star-forming regions, approaching main sequence cluster levels by about ~30 Myr (roughly the pre-main sequence lifetime of a solar mass star). Using new data currently being acquired as part of a large program at the Canada-France-Hawai'i Telescope we will model the coronal evolution of pre-main sequence stars, and produce a theoretical grounding for the observed evolution of their rotation-activity relationship.
Triggering of star formation
Bonnell, Prof Ian - iab1@st-andrews.ac.uk

There are several outstanding issues in current models of star formation. One of these is the role of feedback from young stars in producing subsequent generations of young stars. Triggering of star formation through supernova events is likely to be the dominant mechanism. Numerical simulations of SNII impacting on molecular clouds and the triggering of star formation will be used to develop physical models, and ultimately observational predictions and tests of the process.
Unlocking the potential of the next generation of galaxy redshift surveys
Tojeiro, Dr Rita - rmftr@st-andrews.ac.uk
Weijmans, Dr Anne-Marie - amw23@st-andrews.ac.uk
Wild, Dr Vivienne - vw8@st-andrews.ac.uk

-> This project qualifies as an STFC studentship in Data-Intensive Science. <-

The Dark Energy Spectroscopic Instrument survey will gather spectra for many millions of galaxies over 14,000 sq. degrees of sky. The size and depth of DESI, particular the Bright Galaxy Survey, will allow us to study the large-scale structure and detailed local environment of each galaxy with unprecedented accuracy. Combined with careful spectral analysis of galaxies, which tells us about its formation history, chemical enrichment and dust content, we will be able to link the evolution of galaxies with their cosmological and local environment with unprecedented clarity.

However, current spectral analysis techniques, although successful, rely on much higher signal to noise data than will be delivered by DESI.

In the regime where we have very many N spectra of low S/N, you will explore forward-modelling techniques, whereby model populations of galaxies are forward-modelled through a survey’s window function, which includes selection and observational effects such as target selection, photon-noise, foregrounds, etc. In that regime, we are interested in recovering the mean physical properties of a set of M galaxy populations, where M << N (see Montero-Dorta et al. 2016 for a simplified application to another dataset). The potential of this technique lies in the fact that the redshift evolution of the galaxy populations may be measured in a completely self-consistent way, using a hierarchical Bayesian approach. In addition you will explore simpler, fully data-driven techniques to recover a mean signal from noisy data. This is a well-studied problem in applied statistics. Often called denoising or signal reconstruction algorithms, such methods work by either filtering (e.g., using wavelets); Gibbs sampling (e.g., Wandelt 2004 for a CMB-motivated approach); or noise subtraction (a common technique in speech recognition).

You will then be able to study the detailed evolution of galaxies within the intricate context of their environment, which will be beautifully characterised by DESI.

This project will suit a student with a keen interest in data analysis, algorithm development, applied statistics and data science.

Please contact Dr Rita Tojeiro, the lead supervisor for this project, for further information.

References:
The DESI survey: https://arxiv.org/abs/1611.00036v1
Montero-Dorta et al. 2016, MNRAS, 461, 1131
Wandelt 2004, arXiv:astro-ph/0401623

Unraveling accretion geometries in young stars
Wood, Dr Kenny - kw25@st-andrews.ac.uk

Currently popular models for the formation of stars like the Sun invoke accretion along magnetic field lines from a protoplanetary disk onto hot spots on the stellar surface. This star-disk model can explain the observed infrared emission from disks and also the ultraviolet excess emission produced from shocks of accreting material impacting the stellar surface. Young stars also display multi-wavelength variability on a wide range of timescales, again attributed to the accretion geometry. The on-going YSOVARS observing campaign is obtaining vast optical and infrared datasets on young stars revealing the complexities of their temporal variability. The goal of this PhD project is to use detailed three dimensional Monte Carlo radiation transfer simulations to model the observed multiwavelength data from the YSOVARs project. Working together with Kenny Wood and Aleks Scholz at St Andrews and in collaboration with members of the YSOVARS team in California, the student will explore different classes of variability and the different star-disk-magnetic field configurations that produce the observed light curves. By modeling data from the vast YSOVARs archive, we will learn about magnetic accretion geometries, disk warping, and the accompanying variability on a range of different time and spatial scales, all contributing to a greater understanding of the star formation process.

Informal enquiries to Kenny Wood: kw25@st-andrews.ac.uk
Warm chemistry in the planet-forming region of protoplanetary discs with JWST
Woitke, Dr Peter - pw31@st-andrews.ac.uk

Carr & Najita (2008) have established that class II T Tauri stars usually exhibit rich molecular emission spectra of H2O, OH, CO2, HCN and C2H2. These emissions are often superpositions of many (up to hundreds of) individual emission lines. JWST/MIRI and, in the future SPICA/SMI, will observe protoplanetary discs with unprecedented spectral resolution and signal/noise.

In the frame of the supervisor's FP7 project "DIANA" we have developed the new fast line tracer FLiTs (yet unpublished work) which can compute formal solutions of the line radiative transfer problem for tens of thousands of spectral lines simultaneously, including the Keplerian velocity fields and physical line overlaps. These line radiative transfer calculations are based on ProDiMo (Woitke et al.2009) thermo-chemical disc models, which compute the chemical abundances and temperatures of gas and dust.

These two developments allow us to harvest future JWST and SPICA line observations of discs. Our models predict these lines fully consistently with the calculated 2D disc structures, which is a much
more powerful approach than previously used parametric LTE-slab models.
The science questions are

* What are the element abundances, and what is the molecular composition of the gas in the planet-forming regions of protoplanetary discs?
* Why do some T Tauri stars show strong molecular emission lines whereas others don’t? Why do Herbig Ae stars show weaker line emissions?
* Can we use IR molecular emission lines to determine the spatial disc structure and diagnose disc anomalies such as gaps, vortices and spiral waves at radial distances of a few AU?
* Can we conclude about dust opacities and gas/dust ratios in the planet forming region?


Condensed Matter

Atomic-scale imaging of magnetism and superconductivity in iron pnictides
Wahl, Dr Peter - gpw2@st-andrews.ac.uk

In many unconventional superconductors, magnetism and superconductivity occur in close proximity to each other - which is surprising given that they are usually considered mutually exclusive properties of a material. This is also true for the iron pnictide superconductors, where in several materials magnetism and superconductivity appear to coexist from macroscopic measurements. In this project, you will take an atomic scale view at the magnetic order and the properties of the superconducting properties using low temperature spin-polarized scanning tunneling microscopy[1]. Combining images of the magnetic order with a characterization of superconductivity from tunneling spectroscopy will allow to establish whether magnetism and superconductivity coexist microscopically, or whether they are really competing. These results provide important benchmarks for theory, and may help to improve our understanding of superconductivity in these materials.

You will be using bespoke low temperature scanning tunneling microscopes, which are installed in a new ultra-low-vibration facility at the University of St Andrews.

[1] Enayat et al., Science 345, 653 (2014).
Local control and manipulation of electronic properties of transition metal oxide surfaces
Wahl, Dr Peter - gpw2@st-andrews.ac.uk

Transition metal oxides host a wide range of physical properties and functionalities, making them an ideal platform for implementing potential future devices. The aim of this project is to establish novel ways to manipulate the local properties of transition metal oxides by using a scanning tunneling microscope to enable writing device structures at the atomic scale into the surface of the material. To establish the properties of these written device structure, you will first use scanning tunneling spectroscopy, but later also explore possibilities to contact the written structures macroscopically to study transport through these and enable actual device operation.
While initial studies will be performed on bulk material, it is envisioned that at later stages of the project, thin-film samples grown by reactive oxide molecular beam epitaxy will be used.
Quantum Critical Points in Ferroelectrics
Scott, Prof Jim - jfs4@st-andrews.ac.uk

When crystals undergo phase transitions at or near zero degrees Kelvin their dynamics differ from those at higher temperatures. Entropy is still involved but arises from quantum mechanical uncertainty, rather than classical effects; this mixes together spatial and temporal fluctuations. Most systems studied thus far involve ferromagnetism or superconductivity, but some work [1,2] has been done by Scott on ferroelectrics. In a pseudo-cubic structure such as SrTiO3 or KTaO3 the main effect is that the isothermal electric susceptibility (dielectric constant) varies as 1/T-squared, rather than the classic Curie-Weiss 1/T, and the effective dimensionality is d+1 = 4. But in highly uniaxial materials, the effective dimensionality is d+1 = 5, which results in the dielectric constant varying exactly as 1/T-cubed [3].

We have recently demonstrated that in the uniaxial materials BaFe12O19, SrFe12O19, and PbFe(12-x)Ga(x)O3. The Ba-isomorph is the most profitable magnetic material in Nature, with £2 billion in sales every year (a few grams for every person on Earth!), primarily as the magnetic stripe material for credit cards. Therefore, although this project is unapplied, it is related to device materials of great commercial interest.

[1] S. E. Rowley et al., Nature Physics (2014)
[2] S. E. Rowley et al., arXiv condmat (2014)
[3] D. Khmelnitskii, JETP Lett. (2014)

The thesis work will not involve growing crystals (they are already in hand) nor building a lab; most of the kit is already operational in Dr. F. Morrison's lab in the School of Chemistry. However, a relatively sophisticated level of data analysis and modelling will be encouraged. Therefore although the project is experimental, students with a high level of interest in theory might find it attractive.

It is probable that summer salary would be available for a PhD student wishing to begin in June or July.
Real space imaging of complex magnetic phases and quantum critical matter
Wahl, Dr Peter - gpw2@st-andrews.ac.uk

Quantum materials often exhibit intricate magnetic orders, and small changes of a tuning parameter such as doping or magnetic field can lead to rather dramatic changes in the macroscopic properties and the magnetic order of the materials. In this project, you will use spin-polarized low-temperature scanning tunneling microscopy and spectroscopy to characterize magnetic order in quantum materials in real space.
This work will build on initial studies by the group which have demonstrated imaging of magnetic order in quantum materials [1,2]. Applying this technique to metamagnetic materials will enable to characterize how magnetic order emerges at a quantum critical point, and what the influence of disorder is. Further it will provide atomic-scale information about the interplay between competing orders, such as magnetic order and charge order and the electronic structure.

You will be using bespoke low temperature scanning tunneling microscopes, which are installed in a new ultra-low-vibration facility at the University of St Andrews.

[1] Enayat et al., Science 345, 653 (2014).
[2] Singh et al., Phys. Rev. B 91, 161111 (2015).
Room-temperature Multiferroics
Scott, Prof Jim - jfs4@st-andrews.ac.uk

Multiferroics are usually defined as crystals that are simultaneously ferromagnetic and ferroelectric. Most are also magnetoelectric, meaning that their magnetization M can be switched by applied electric field and their polarization P switched via applied magnetic field H.

This PhD thesis project will emphasize the materials GaFeO3 and its isomorphs, as well as PbFe(1/2)Nb(1/2)O3 and related Ta, Ti, and Nb compounds.

The thesis work will not involve growing crystals (they are already in hand) nor building a lab; most of the kit is already operational in Dr. F. Morrison's lab in the School of Chemistry. However, a rewlatively sophisticated level of data analysis and modelling will be encouraged. Therefore although the project is experimental, students with a high level of interest in theory might find it attractive.

It is probable that summer salary would be available for a PhD student wishing to begin in June or July.
Superconductivity in Non-Centrosymmetric Materials and Structures
Wahl, Dr Peter - gpw2@st-andrews.ac.uk

The aim of this project is to investigate experimentally the influence of broken inversion symmetry on superconductivity in a variety of non-centrosymmetric (NCS) materials.
Most crystalline metals have a structure that maps onto itself exactly under inversion of spatial coordinates. Such materials are termed “centrosymmetric” and when they become superconducting, the spatial part of the Cooper pair wavefunction must have a definite parity, i.e. inversion simply multiplies it by ±1. This imposes restrictions also on the spin configuration within the Cooper pair. By contrast, in non-centrosymmetric superconductors where the crystal structure breaks inversion symmetry, such restrictions do not apply. Amongst the properties predicted for non-centrosymmetric superconductors are mixed spin-singlet/spin-triplet pairing, enhanced critical fields and spatially modulated superconducting states. Whilst unusual superconducting properties have been detected in a number of NCS materials, there is relatively little firm experimental evidence linking these to the lack of inversion symmetry; for example only in very few cases has a substantial triplet component of the order parameter been firmly established.
The project will be focused on NCS superconductors where the electronic correlations are weak, since these offer the chance to isolate the role of the broken inversion symmetry. The experiments will focus on using low temperature scanning tunneling microscopy and spectroscopy to establish the structure of the superconducting order parameter and study the influence of defects of different dimensionalities on the superconducting properties.
2D Quantum Materials
King, Dr Phil - pdk6@st-andrews.ac.uk

As part of a generously-funded research project from the Leverhulme Trust, we are seeking ambitious and motivated PhD students to join a major research initiative aimed at investigating the electronic structure and collective states of two-dimensional quantum materials. The remarkable electronic, optical, and structural properties of graphene, a single atom-thick layer of carbon, has spurred enormous interest in 2D materials. In this project, you will seek to develop 2D materials, and their combinations, which incorporate the effects of pronounced electronic interactions, focusing on transition-metal dichalcogenide (TMD) compounds. Bulk TMDs are known to support a wide variety of striking physical properties such as superconductivity and charge density-wave states, but how these are modified when the material is restricted to just a single layer in thickness are only just starting to be explored, and combining strongly-interacting 2D materials in different configurations and environments promises a huge array of exciting possibilities to stabilise rich phase diagrams and unique properties. The work undertaken will build on the group’s existing activity in the study of TMDs, strong spin-orbit, topological, and interacting electron systems [1-6], and ultimately aims to develop new routes towards the “on-demand” control of the quantum many-body system underpinning the physical properties of 2D quantum materials. Projects are available developing the growth of single monolayers and heterostructures of TMD compounds using a recently-installed state-of-the art molecular-beam epitaxy system in St Andrews and utilizing a linked system for angle-resolved photoemission spectroscopy, as well as further ARPES and spin-resolved ARPES work at international synchrotrons, to probe the resulting electronic structure and many-body interactions of the materials synthesized. There are also possibilities to spend extended research visits with our collaborators in Tokyo and in Italy. As part of this project, you will undertake experiments at national and international facilities. Thus, a willingness to travel is an essential prerequisite. For further information, or to discuss specific research possibilities, please contact philip.king@st-andrews.ac.uk.

[1] King et al., Nature Comm. 5 (2014) 3414
[2] King et al., Nature Nano. 9 (2014) 443
[3] Riley et al., Nature Physics 10 (2014) 835
[4] Riley et al., Nature Nano. 10 (2015) 1043
[5] King et al., PRL 107 (2011) 096802
[6] Bawden et al., Science Advances 1 (2015) 1500495
Ambient pressure photoemission spectroscopy of organic semiconductor devices
Turnbull, Prof Graham - gat@st-andrews.ac.uk

Ambient pressure photoemission spectroscopy is a new technique to measure the energy levels of materials. Combined with scanning Kelvin probe spectroscopy APS can provide information about the electronic properties of thin film materials relevant to LEDs, solar cells, sensors and lasers. The aim of this project will be to combine measurements of the energy levels of organic semiconductors to understand their operation in optoelectronic devices.

The HOMO and LUMO levels of organic semiconductors are crucial to charge injection, exciton formation, energy transfer and charge transfer in OLEDs, solar cells, lasers and chemical sensors. Currently the standard measurement to determine energy levels is cyclic voltammetry but this is typically used to measure individual molecules in solution, and there would be a lot of advantage if we could measure directly the materials int he solid-state including thin films as used in devices.

Applications of these measurements would be to better understand the operation of solar cells, OLEDs and thin film chemical sensors.
Artificial quantum materials
King, Dr Phil - pdk6@st-andrews.ac.uk
Wahl, Dr Peter - gpw2@st-andrews.ac.uk

The epitaxial compatibility of many oxides which, in bulk form, host an extraordinarily wide array of physical properties opens almost limitless possibilities for creating new artificial materials structured at the atomic scale [1]. Recent advances in atomically-precise deposition techniques have opened new potential to manipulate the properties of these ubiquitous but still poorly-understood materials [2], creating new "designer" compounds with tailored properties not found in bulk. You will exploit a brand new £1.8M growth facility to build up transition-metal oxide materials one atomic layer at a time, exploiting tuning parameters such as epitaxial strain and the layering of disparate compounds to selectively tune their functional properties. To provide direct feedback on how this influences the underlying quantum states in these complex materials, you will employ advanced spectroscopic probes such as angle-resolved photoemission [3] or scanning tunneling microscopy and spectroscopy [4], utilizing our state-of-the-art capabilities in St Andrews. Together, this promises new insight into the rational design of quantum materials and their potential for future quantum technologies.

[1] J. Mannhart and D. Schlom, Science 327, 1607 (2010).
[2] P.D.C. King et al., Nature Nano. 9, 443 (2014).
[3] J.M. Riley et al., Nature Phys. 10, 835 (2014).
[4] M. Enayat et al., Science 345, 653 (2014).
Collective excitations of correlated and spin-orbit coupled quantum materials
King, Dr Phil - pdk6@st-andrews.ac.uk

A key goal of condensed matter physics is to develop a thorough understanding of the microscopic properties of materials to enable the rational design of new compounds with desired characteristics. A major challenge, however, is that their particles often do not act independently, but collectively. This collective behavior can have striking consequences, such as superconductivity and magnetism, but can be challenging to probe experimentally and understand theoretically. In this project, you will initially develop a state-of-the-art instrument to probe the inelastic scattering of low-energy electrons, opening exciting new opportunities for studying the collective excitations in materials with unprecedented resolution. You will apply this to investigate exotic metals known to exist at the surface of a special type of insulator called a topological insulator [1] as well as correlated quantum states in designer quantum materials [2]. This will provide new insights on their collective excitation spectra and many-body interactions, key to understanding their physical properties.

[1] King et al., Phys. Rev. Lett. 107 (2011) 096802
[2] King et al., Nature Nano. 9 (2014) 443
Controlling emergent quantum phases through strain-tuning of electronic structure
Hicks , Dr Clifford - cwh10@st-andrews.ac.uk
King, Dr Phil - pdk6@st-andrews.ac.uk
Mackenzie, Prof Andy - apm9@st-andrews.ac.uk

The strong interactions at the heart of correlated electron materials yield striking collective states such as superconductivity or magnetism, and often mediate giant responses to small external perturbations. This offers unique opportunities to tune these subtle quantum many-body systems, to shed new light on their underlying physics and ultimately to engineer desired functional properties. In this project, you will exploit externally-applied and continuously-tunable mechanical strain in an attempt to harness control over emergent phases in correlated solids, for example tuning unconventional superconductivity in Sr2RuO4 and controlling quantum criticality in Sr3Ru2O7. You will perform low-temperature transport measurements as a function of uni- and bi-axial strain using custom apparatus within the world-leading facilities of the Max-Planck Institute for the Chemical Physics of Solids in Dresden, Germany. You will also design similar apparatus that can be integrated within our state-of-the-art system for angle-resolved photoemission (ARPES) in St Andrews, as well as in ARPES systems at synchrotron light sources within the UK, Europe and the USA. This will allow you to track the corresponding electronic structure changes that control the materials’ transport and thermodynamic properties with unprecedented detail. This project is offered as part of a Max Planck – CM-DTC initiative (http://cm-dtc.supa.ac.uk/research/max%20planck.php). You will spend part of your time performing research in MPI Dresden (with Dr. Hicks & Prof. Mackenzie), part in St Andrews (with Dr. King), and will also undertake experiments at national and international facilities. Thus, a willingness to travel is an essential prerequisite. Collaborations in this area are also envisaged with the STM group of Dr. Peter Wahl in St Andrews.
Decoherence of quantum registers
Lovett, Dr Brendon - bwl4@st-andrews.ac.uk

Quantum computing has undergone something of a revolution in recent years. From being a technology that only a few thought might be ever be realized, a small scale computing device is now a realistic target in the next five years.


This has been driven by remarkable recent progress in both theory and experiment. In particular, it is now established that the coherence time of single qubits in solid state systems is many orders of magnitude longer than that required to execute a simple logic gate.


The timing is now perfect to develop a detailed blueprint for how to scale up from one to many qubits. In particular, we must gain a detailed understanding of how to describe a system of several coupled qubits interacting with a common environment. In this situation, many of the more straightforward approximate approaches to modelling open quantum systems fail. You will therefore exploit more sophisticated, and accurate, methods, such as those based on Feynman’s path integral formulation of quantum mechanics, to make predictions about the dynamics of quantum registers.


Emergent Order in Hybrid Photon-Atom Systems
Braunecker, Dr Bernd - bhb@st-andrews.ac.uk

Novel self-ordered phases can emerge in a conductor with interacting electrons and embedded magnetic moments [1,2]. This is quite surprising because the energy and time scales of the considered magnetic moments (e.g., nuclear spins) differ by orders of magnitude from those of electrons. Yet, within this decoupling of scales, the ordering mechanism is general and not bound to specific materials. Quite remarkably such self-ordered phases have made recently a strong link with the currently much discussed physics of topological superconductors and Majorana bound states [3].

In this PhD project, we shall explore systems in which the time and energy scales are turned upside down, notably, in which the effective interaction that triggers the order travels at a turtle's pace. This is an extreme limit in which this slow dynamics will play a further important role. For a definite example we will focus on cavity photons that are coupled through an interacting atomic gas, which is of the type of systems that are under investigation, for instance, in the group of Prof Jon Simon at the University of Chicago (http://simonlab.uchicago.edu).

[1] B. Braunecker, P. Simon, and D. Loss, Phys. Rev. Lett. 102, 116403 (2009) [arXiv:0808.1685].
[2] B. Braunecker, P. Simon, and D. Loss, Phys. Rev. B 80, 165119 (2009) [arXiv:0908.0904].
[3] B. Braunecker and P. Simon, Phys. Rev. Lett. 111, 147202 (2013) [arXiv:1307.2431].
Energy Transfer Networks
Lovett, Dr Brendon - bwl4@st-andrews.ac.uk

Recent experiments on photosynthetic complexes reveal the possible presence of quantum coherence between excitations on different parts of the protein complexes involved. It has been conjectured that these quantum correlations may lead to enhanced energy transfer, and thus to more efficient solar cells.

In this project, you will explore the interplay of quantum and classical mechanisms for moving electronic energy around networks of molecules. On the one hand, quantum correlations can lead to constructive interference between different parts of the network, leading to a faster transport of energy. On the other hand, such correlations may lead to destructive interference, and cause excitations to get stuck. Classical hopping may relieve this problem. You will predict the optimal balance of classical and quantum processes that lead to the highest rate of energy extraction from the network. You may need to explore the role of length scale, network topology, and use thermodynamic concepts to address this problem.

The project will be in collaboration with theorists at the University of Oxford, and may be tested in the laboratories of collaborators both in St Andrews, and at the Universities of Oxford and Cambridge.
Exciton Diffusion in Organic Semiconductors
Samuel, Prof Ifor - idws@st-andrews.ac.uk

The discovery of semiconducting properties in organic materials has opened major new directions in semiconductor physics. Organic semiconductors combine the simple fabrication and tuning of properties that is typical of plastics with novel optoelectronic properties useful for devices such as light-emitting diodes and solar cells. The low-dimensional nature of these materials means that excitons (electron-hole pairs) are strongly bound even at room temperature and play a very important role in their physics. Whilst charge transport has been widely studied, exciton transport has been largely overlooked. We have now developed techniques based on time-resolved spectroscopy that allow the measurement of exciton diffusion. We now wish to apply them to understand the physics of exciton diffusion and the factors controlling it. A breakthrough in this field could in turn lead to a breakthrough in the efficiency of organic solar cells.
Experimental and Theoretical Investigation of Spatially Modulated Magnetic Phases Near to Quantum Criticality
Huxley, Prof Andrew - ah311@st-andrews.ac.uk

The possibility of magnetic spin-crystals formed by the superposition of helical spin modulations with different wave-vectors has been a subject of much recent experimental and theoretical work. Signatures of phases with this property have been found in an array of materials including MnSi and Sr3Ru2O7. On the theoretical side, there are several ways in which such states might form. These include the formation of spiral modulation due to a Dzyalosinskii-Moriya spin-orbit interaction in itinerant magnets, residual, small-wavevector nesting due to the electron dispersion in a lattice [1,2] and from competing interactions that can give rise to a series of transitions forming a Devil's Staircase [3]. Perhaps the most intriguing suggestion - and one that has most captured the imagination of condensed matter theorists of late - is that an itinerant system on the brink of a quantum phase transition might possess an intrinsic instability to the formation of modulated magnetic phases [4]. In any particular material, one or more of these effects may operate with the possibility of a complicated interplay between them.

This project aims to investigate the phenomenon of spatially modulated magnetism from both an experimental and theoretical perspective. We will use techniques of quantum many-body physics and field theory to investigate the possibility of spatially modulated magnetism in real systems. These investigations will be carried out in concert with neutron scattering experiments to provide inspiration for and validate this theory. The experimental part will include growing the crystals for these experiments as well as performing the measurements. We anticipate that a student will spend approximately 2/3 of their time on theory and 1/3 on experimental work, working both in Edinburgh and St Andrews as well as at international facilities.

[1] A. M. Berridge, A. G. Green, S. A. Grigera and B. D. Simons "A Magnetic Analogue of the of the FFLO state: Inhomogeneous Instabilities Near to Tricritical Points" Physical Review Letters 102, 149903 (2009).
[2] G. J. Conduit, A. G. Green, and B. D. Simons, "Inhomogeneous phase formation on the border of itinerant ferromagnetism" Physical Review Letters 103, 207201 (2009) [spotlighted in Physics 2, 93 (2009)]
[3] P. Bak & J. von Boehm, "Ising model with solitons, phasons, and 'the devil's staircase'", Phys Rev B 21 5297 (1980)
[4] J. Rech C.Pépin, V.Chubukov, "Quantum critical behaviour in intinerant electron systems: Eliashberg theory and instability of a ferromagentic quantum critical point" Phys Rev B 74 195126 (2006)
Finite-temperature behaviour of quantum Kasteleyn systems
Hooley, Dr Chris - cah19@st-andrews.ac.uk

Recent work on the so-called ‘spin ice’ materials [1] has produced a resurgence of interest in Kasteleyn transitions [2]. In a typical demagnetisation transition, the magnetism of a sample is reduced by the formation of local domains of flipped spins. In a Kasteleyn transition, however, these are effectively forbidden, and the transition is driven instead by the appearance of lines of flipped spins that extend all the way from one side of the sample to the other.
The standard theory of these transitions is purely classical, with the transition being driven by increasing temperature. But it is interesting to ask whether there is a quantum version of such a transition, driven by (for example) a transverse magnetic field [3]. If so, it should give rise to interesting finite-temperature phenomena: the Kasteleyn analogues of the quantum criticality observed in the conventional case [4].

The initial goal of this project is to determine whether a quantum Kasteleyn transition exists in a particular toy model [3], and then to develop a theory of the finite-temperature behaviour of the model in the vicinity of the quantum Kasteleyn point.

[1] C. Castelnovo, R. Moessner, and S.L. Sondhi, Nature 451, 42 (2008).
[2] L.D.C. Jaubert, J.T. Chalker, P.C.W. Holdsworth, and R. Moessner, Phys. Rev. Lett. 100, 067207 (2008).
[3] S.A. Grigera and C.A. Hooley, arXiv:1607.04657.
[4] S. Chakravarty, B.I. Halperin, and D.R. Nelson, Phys. Rev. B 39, 2344 (1989).

Category: Theoretical Hard Condensed Matter
Holographic traps and guides for superfluidity studies and atom interferometry
Cassettari, Dr Donatella - dc43@st-andrews.ac.uk

Holographic traps are a new kind of optical traps for neutral atoms which are promising for a wide range of applications, e.g. quantum information processing and quantum simulation. They are produced by diffracting a laser beam off a computer-controlled optical device, known as a Spatial Light Modulator (SLM). This apparatus offers unparalleled flexibility in the choice of trapping geometry, and different experiments can be done simply by reconfiguring the SLM.
In this PhD project you will work on:

- Double well traps for confined atom interferometry, which is promising for the development of sensitive devices (see [1] for a review).

- Ring-shaped atom guides (see [2] and [3]), which can be used to observe superfluid motion of a Bose-Einstein condensate, e.g. persistent current states. BECs in these geometries and the study of their critical velocities (where superflow stops) have very important technological applications in sensing devices, such as superconducting quantum interference devices (SQUIDs). Moreover, theoretical proposals have been put forward in which coherent superposition of different BEC flows can be used as qubits.

[1] http://rmp.aps.org/abstract/RMP/v81/i3/p1051_1
[2] http://prl.aps.org/abstract/PRL/v106/i13/e130401
[3] http://lanl.arxiv.org/abs/1008.2140
Holographic traps for the efficient production of Bose-Einstein condensates
Cassettari, Dr Donatella - dc43@st-andrews.ac.uk

Evaporative cooling is an essential stage in the creation of Bose-Einstein condensates (BECs) in atomic gases. Recently we suggested [1] that holographic optical traps can be used to increase the evaporation efficiency, leading to larger BECs. In this PhD project you will implement this scheme, which will result in a simplified apparatus for the productions and subsequent manipulation of BECs.

[1] http://pra.aps.org/abstract/PRA/v84/i5/e053410

Integrated Magnetic Resonance Doctoral Training Centre
Smith, Dr Graham - gms@st-andrews.ac.uk

The new EPSRC Doctoral Training Centre in Integrated Magnetic Resonance is a collaboration between 6 of the UK's leading Universities in Advanced Magnetic Resonance Instrumentation and Techniques and includes St. Andrews, Dundee, Aberdeen, Warwick, Nottingham and Southampton.

The aim is to provide a coherent training program for doctoral students whilst working on new research topics in instrumentation and methodology, associated with Magnetic Resonance Imaging, Electron Magnetic Resonance, Nuclear Magnetic Resonance and Dynamic Nuclear Polarisation (which collectively represent £multi-Billion annual markets). Training is delivered from all centres, through residential workshops and over the Access Grid, primarily in the first two years of study.

Funded 4 year PhDs include fees and maintenance of £14000 (tax free) per annum as well as an enhanced travel budget. All PhDs will have internal and external mentors from other centres.

At St Andrews, PhD projects are available on themes associated with major advances in Electron Magnetic Resonance and Dynamic Nuclear Polarisation and are likely to involve collaborations with other centres and other interdisciplinary groups.

PhD topics are likely to involve a combination of instrumental, methodological and computational techniques that would normally be associated with Basic Technology programs.

Representative PhDs from all 6 centres are listed on www.imr-cdt.ac.uk, but other PhD topics may be available on request.

For PhDs at St Andrews, applications can be made directly to St Andrews or via Warwick where the DTC program is administered.
Investigating novel superconducting ground states in nanofabricated hybrid ferromagnetic-superconducting materials and devices using advanced neutron, muon and synchrotron techniques
Lee, Prof Steve - sl10@st-andrews.ac.uk

The search for novel quantum states of matter in artificial thin-film structures, in which superconducting (S) and ferromagnetic (F) materials are juxtaposed, has reached an exciting and timely stage of development. In the last year a series of new landmark experimental results seem set to herald a period of rapid expansion of interest and activity in the field. This was the pioneering observation by several groups of spin-triplet supercurrents traversing relatively thick F layers [1-3], believed theoretically to be signatures of a novel equal-spin spin-triplet and possibly ‘odd frequency’ superconducting state. This achievement represent the culmination of several years of breakthrough experiments [1-7] in a field whose modern era began almost most a decade ago, with the experimental discovery of Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) [8] type states in S-F-S structures [10]. What both the FFLO [8] and the odd-frequency pairing phenomena [9] have in common is that they were predicted to occur theoretically in bulk systems [8,9] but only in state-of-the-art artificial thin-film structures were they finally demonstrated to exist [1-7,10-13]. Modern thin-film growth and large area lithographic patterning open-up an enormous range of further possibilities for engendering novel quantum states of matter via the controlled interaction S and F order on the nanoscale. This capability also offers the promise of designing and engineering hybrid metamaterials (in a similar spirit to electromagnetic metamaterials) with tailored quantum properties. Concurrently there is enormous interest in spintronics, the manipulation of electronic spin for application in novel electronic devices. The structures investigated within this programme marry the fields of mesoscopic superconductivity, novel strongly correlated electron physics and spintronics. By introducing quantum coherence phenomena into spintronic types devices, this also opens up the possibility of non-locality and entanglement, with possible application long-term in quantum computation.

Professor Steve Lee leads an EPSRC funded Critical Mass Grant award (St Andrews, Leeds, Bath, Royal Holloway, ISIS, with partners in PSI ( Swizterland), Cambridge, and Leiden ) that underpins an international research programme that brings together a team with a wide range of relevant expertise to explore the physics of such systems. We make use of some of the most powerful probes in condensed matter physics (scattering and surface probe techniques) in order to throw new light onto the physics of artificial S-F metamaterials, with particular emphasis on spatially–resolved measurements. This combines with state-of-the-art facilities for materials growth and patterning and world leading instrumentation for measurement. The programme is also informed by cutting-edge theory. There are significant opportunities for research students within this collaboration, with excellent access to world leading research facilities (such as Diamond, ISIS, ILL, PSI, SLS). Due to the strong interactions between nodes there is also significant scope for student mobility in order to enhance training and experience. This is all underpinned by access to excellent graduate training bot via the SUPA Graduate School and the additional benefits of the Doctoral Training Centre in condensed matter physics based at St Andrews, Edinburgh and Heriot Watt.

[1] J.W.A. Robinson et al., Science 329 59 (2010).
[2] T.S. Khaire et al., PRL 104, 137002 (2010).
[3] M.S. Anwar et al., PRB 82, 100501 (2010).
[4] R.S. Keizer et al., Nature 439 825 (2006).
[5] J. Wang et al., Nat. Phys. 6 389 (2010).
[6] I. Sosnin et al., PRL 96 157002 (2006).
[7] D. Sprungmann et al., PRB 82, 060505 (2010).
[8] P. Fulde and R.A. Ferrell, PRB 135 A550 (1964);
A.I. Larkin and Y.N. Ovchinnikov, Zh. Eksp.
Teor. Fiz. 47, 1136 (1964).
[9] V.L. Berezinskii, JEPT Lett. 20, 287 (1974).
[10] V.V. Ryazanov et al., PRL 86, 2427 (2001); T. Kontos et al., PRL 89, 137007 (2002).
[11] A.I. Buzdin et al., JETP Letters 35, 178 (1982);
[12] F.S. Bergeret et al., PRL 86, 4096 (2001); Rev. Mod. Phys. 77, 1321 (2005).
[13] M. Eschrig et al., PRL 90, 137003 (2003); M. Eschrig and T. Löfwander, Nature Phys. 4 138 (2008).


Magnetic measurements to probe unconventional superconductors
Huxley, Prof Andrew - ah311@st-andrews.ac.uk
Yelland, Dr Ed - eay1@st-andrews.ac.uk

Magnetism and superconductivity are intimately connected in many so-called heavy fermion metals. A particularly dramatic case is URhGe, where two distinct superconducting regions exist – one coexisting with ferromagnetism, and the other at extremely strong applied magnetic fields that are sufficient to destroy conventional forms of superconductivity. This project will involve developing sensitive magnetic measurement apparatus that will operate at extremes of low temperature, high magnetic field and high pressure, and apply them to study URhGe and other related materials. The aims are both to gain a deeper understanding of how magnetic pairing may lead to superconductivity and to drive the search for new superconducting materials. The project could be based in either St Andrews or Edinburgh.

The project is an integral part of a major research effort to study quantum criticality and unusual quantum ordered phases using a variety of magnetic, electrical and thermal measurement techniques. The apparatus in St Andrews includes a state-of-the-art dilution refrigerator (commissioned December 2007) with a base temperature 10 millikelvin and equipped with a 17 tesla magnet, that will allow coverage of a wide region of experimental parameter space, including applied pressures up to 100 kbar.

The focus for the project is on magnetic measurements including torque magnetometry, field gradient magnetometry and a.c. susceptibility. By combining torque and field-gradient results, the vector magnetic moment can be determined as a function of magnetic field and its angle to the crystallographic axes. This will allow a complete phenomenological (Ginzburg-Landau) description of the magnetism close to the superconducting phase to be constructed, and will provide detailed information about the nature of the magnetic interactions that are important for superconductivity. Another important component of the work will be to use quantum oscillations in various magnetic quantities to study the Fermi surface and how these change approaching and crossing quantum phase transitions.
Manipulating electron spins to explore structure in biomacromolecules.
Lovett, Dr Janet - jel20@st-andrews.ac.uk

Knowledge of the structure of and structural changes within biomacromolecules such as proteins or oligonucleotides (DNA, RNA) leads to advancing our understanding of the underlying mechanisms of function. Ultimately this is not only fundamentally interesting but will lead to improved drug targets and better biotechnology.

Electron paramagnetic resonance (EPR) spectroscopy is capable of measuring nanometre distances between stable radicals, such as nitroxyl-containing spin labels.[1] These spin labels can be attached site-selectively to proteins or nucleic acids, though naturally occurring paramagnetic centres can also be used.[2,3] For example, double electron electron resonance (DEER) is a pulsed EPR experiment that has proved useful for studying the structure of a range of biomacromolecules.1,4 Many of these experiments have been carried out in frozen glassy solutions. Your project would be to work on methods to expand the scope of the environment that biopolymers can be studied in through development of high-pressure,[5] room temperature[6] and in-cellular methods.[7]

The PhD will be run through the School of Physics and Astronomy at the University of St Andrews and you will also be a member of the Biological Sciences Research Complex. You must have a good scientific degree for example in a such as chemistry, biochemistry, biology or physics and be motivated to work across the disciplines.

The facilities at St Andrews for EPR, protein preparation and chemistry are outstanding, more information can be found at http://www.st-andrews.ac.uk/~jel20. Informal enquires are encouraged prior to application and should be made to Dr Janet Lovett (jel20@st-andrews.ac.uk).


1. Klare, J. P. and Steinhoff H.-J., (2009) Photosynth Res 102 377-390
2. Haugland, M. M., El-Sagheer, A. H., Porter, R. J., Pena, J., Brown, T., Anderson, E. A., Lovett, J. E., (2016) J. Am. Chem. Soc. 138 9069-9072
3. Motion, C. L., Lovett, J. E., Bell, S., Cassidy, S. L., Cruickshank, P. A. S., Bolton, D. R., Hunter, R. I., El Mkami, H., Van Doorslaer, S. and Smith, G. M., (2016) J. Phys. Chem. Lett. 7 1411-1415
4. Jeschke, G., (2012) Annu. Rev. Phys. Chem. 63 419-446
5. Lerch, M. T., López, C. J., Yang, Z., Kreitman, M. J., Horwitz, J. and Hubbell, W. L., (2015) Proc. Natl. Acad. Sci. E2437–E2446
6. Meyer, V., Swanson, M. A., Clouston, L. J., Boratyński, P. J., Stein, R. A., Mchaourab, H. S., Rajca, A., Eaton, S. S. and Eaton G. R., (2015) Biophys. J. 108 1213-1219
7. Igarashi, R., Sakai, T., Hara, H., Tenno, T., Tanaka, T., Tochio, H. and Shirakawa, M., (2010), J. Am. Chem. Soc. 132 8228-8229.

Funding

The studentship will be funded through EPSRC and as such successful applicants from the UK can be fully supported for 3.5 years though there are exceptions, please see https://www.epsrc.ac.uk/skills/students/help/eligibility/ . Funding is allocated depending upon availability and candidate quality so early applications are encouraged.

Citizens of China may be eligible for funding through the China Scholarship Council, https://www.st-andrews.ac.uk/study/international/csc/ . The internal deadline for applications to the School of Physics and Astronomy is the 23rd November 2016.

Mesoscopic unconventional superconductors and Fermi liquids
Mackenzie, Prof Andy - apm9@st-andrews.ac.uk

This project is offer in conjunction with Prof. Amir Yacoby at Harvard.

In this project, we aim to bridge the gap between two fields in which huge progress has been made over the past twenty years. In mesoscopic physics, the aim is to work with samples that are specially fabricated so that their physical size becomes comparable with one or more of the fundamental length scales of the underlying physics. In a metal this might be the mean free path, and in a superconductor it might be the coherence length or the penetration depth. So far, the vast majority of research into mesoscopic physics has been performed on traditional materials in which the electron-electron interactions are relatively weak. In parallel with these developments, equally rapid progress has been made on research into new materials with very strong electron-electron interactions, which lead to high quasiparticle masses and an exciting variety of metallic, superconducting and magnetic ground states. For technical reasons the two fields have advanced in parallel, with little cross-fertilisation of ideas and techniques. The goal of this jointly supervised project is to combine the different expertise of our two groups to bring strongly interacting electrons into the mesoscopic regime. You will work both in St Andrews and at the spectacular new Harvard Nanoscience Center, performing pioneering experiments on the fabrication and measurement of correlated electron mesoscopic devices.

(Jointly affiliated to both University of St Andrews and Max Planck Institute for the Chemical Physics of Solids, Dresden)



Microscopic Phase Coexistence: a Conformal Bootstrap Analysis
Hooley, Dr Chris - cah19@st-andrews.ac.uk

Consider a two-dimensional condensed matter system in which two different low-temperature phases are competing, i.e. where tuning some non-thermal parameter causes a transition from one to the other. For example, the competing phases might be the superfluid and solid phases in a film of helium-4 (the tuning parameter in this case being pressure), or the stripe-ordered and superconducting phases in a cuprate superconductor (with doping as the tuning parameter). Do we expect an abrupt first-order transition from one phase to the other, or might there be an intermediate range of parameters in which the system exhibits both types of order simultaneously? (I don’t mean phase separation, like bubbles of gas in a liquid – I mean that the phases coexist at the microscopic level.)

The answer to this question depends on the symmetry of the ordered phases in question, and in most cases it is known [1]. However, the case where both phases have O(2) symmetry is a more subtle one, and despite recent work [2] is not fully settled. In the past few years an exciting new theoretical tool has become available: the so-called ‘conformal bootstrap’ [3]. The initial aim of this project is to apply the bootstrap method to address the question of phase coexistence in the O(2)+O(2) case. Should this be achieved quickly, studies could be extended to non-zero temperature, where one would expect some interesting Kosterlitz-Thouless-like phase transitions [4,5].

[1] P. Calabrese, A. Pelissetto, and E. Vicari, Phys. Rev. B 67, 054505 (2003).
[2] A. Jaefari, S. Lal, and E. Fradkin, Phys. Rev. B 82, 144531 (2010).
[3] S. El-Showk et al., Phys. Rev. D 86, 025022 (2012).
[4] J.M. Fellows, S.T. Carr, C.A. Hooley, and J. Schmalian, Phys. Rev. Lett. 109, 155703 (2012).
[5] C.A. Hooley, S.T. Carr, J.M. Fellows, and J. Schmalian, JPS Conf. Proc. 3, 016018 (2014).

Category: Theoretical Hard Condensed Matter
Multimode cavity QED, beyond the superradiance paradigm
Keeling, Dr Jonathan - jmjk@st-andrews.ac.uk

Recent experiments on Bose--Einstein condensates in optical cavities have reported a quantum phase transition to a coherent state of the matter-light system -- superradiance[1]. This experiment, and related work following the theoretical proposal [2] has prompted much exploration of the possibilities of cavity QED with ultracold atoms as a venue to explore collective behaviour in open quantum systems.

While experiments on single mode cavities [1,2,3] have been studied extensively, experiments on multimode cavities [5] are only just beginning. These have the potential to transform the kinds of behaviour one can study. We have recently explored the idea of simulating dynamical gauge fields with such a system [6]. Other possibilities suggested include simulating Hopfiled associated memories (including potentially quantum extensions thereof), and liquid crystaline phases of matter. This PhD will explore a number of these topics; we will work in close collaboration with the Lev group in Stanford, so the precise projects will be determined in order to match ongoing and future experiments.


[1] K. Baumann, C. Guerlin, F. Brennecke, and T. Esslinger,
Nature 464, 1301 (2010)
[2] F. Dimer, B. Estienne, A. S. Parkins, and H. J.
Carmichael, Phys. Rev. A 75, 013804 (2007).
[3] M. J. Bhaseen, J. Mayoh, B. D. Simons, J. Keeling. Phys. Rev. A 85, 013817 (2012)
[5] A. J. Kollár, A. T. Papageorge, V. D. Vaidya, Y. Guo, J. Keeling, B. L. Lev
https://arxiv.org/abs/1606.04127
[6] K. E. Ballantine, B. L. Lev, Jonathan Keeling
http://arxiv.org/abs/1608.07246v1
Novel Quantum Order in Vector Magnetic Fields
Mackenzie, Prof Andy - apm9@st-andrews.ac.uk

Strongly interacting electron systems are one of the best hosts for study of the quantum many-body problem. Experimental discoveries made in the past decade show that, in the cleanest materials, a variety of subtle collective states form at low temperatures. Some of these are metallic but involve the development of a preferred direction, driven not by the crystal symmetry but by the electron-electron interactions themselves. To study anisotropic responses like these, careful experiments are necessary – they can easily be missed if the correct probes are not used. Many of the states discovered so far have a coupling to externally applied magnetic fields, so these fields can be used to ‘train’ the systems’ response functions. This has highlighted the need to develop better and better ‘vector magnets’ in which the field vector can be changed via computer-controlled energisation of multiple superconducting coils. On this project you will have access to world-leading instruments capable of generating 1, 1 and 9 tesla along the x, y and z axes. This will enable you to study transport and thermodynamic quantities that cannot be accessed in standard instruments. Using this unique instrumentation, you will have the chance to investigate a range of the most exciting new strongly correlated materials in a fast-moving field of modern research.

(Jointly affiliated to both University of St Andrews and Max Planck Institute for the Chemical Physics of Solids, Dresden)
Polaritons in organic semiconductor microcavities
Samuel, Prof Ifor - idws@st-andrews.ac.uk
Turnbull, Prof Graham - gat@st-andrews.ac.uk

When light is confined on the nanoscale it is possible to observe light-matter interactions that are not normally observed in bulk materials. One example is the strong coupling of photons and excitons in wavelength-scale microcavities which leads to a number of unusual phenomena [1,2]. The modes of the cavity couple with the exciton to make a hybrid-light-matter state called a polariton. One can make polaritons lasers that emit coherent light [3] and it has been shown that polaritons can form a Bose-Einstein condenstate [4].

This project will explore the properties of polaritons in microcavities based on organic semiconductors [2,4-6]. It will involve the fabrication of microcavities that include J-aggregate dyes or semiconducting polymers to explore how the energy states of organic materials can be modified when coupled to the cavity modes, and be applied in photonic devices including lasers and LEDs.

[1] C. Weisbuch et al., Phys. Rev. Lett. 69, 3314 (1992)
[2] D.G. Lidzey et al., Nature 395, 53 (1998)
[3] S. Christopoulos et al., Phys. Rev. Lett. 98, 126405 (2007)
[4] J D Plumhof, T Stöferle, L Mai, U Scherf & R F Mahrt, Nature Materials 13, 247–252 (2014)
[5] T. Schwartz, J. A. Hutchison, C. Genet, and T. W. Ebbesen, Phys. Rev. Lett. 106, 196405 –(2011)
[6] S Kéna-Cohen*, S A. Maier and D D. C. Bradley, Advanced Optical Materials 1, 827–833, (2013)
Quantum Electronic States in Delafossite Oxides
King, Dr Phil - pdk6@st-andrews.ac.uk

As part of a generously-funded ERC research project, we are seeking ambitious and motivated PhD students to join a major research initiative aimed at investigating Quantum Electronic States in Delafossite Oxides (QUESTDO). One of the most active challenges of modern solid state physics and chemistry is harnessing the unique and varied physical properties of transition-metal oxides. While little-studied to date, initial work suggests that the delafossite oxide metals are a particularly rich member of this materials class. They exhibit a wide array of fascinating properties, from ultra-high conductivity [1,2] to unconventional magnetism [3], with the potential to host strongly spin-orbit coupled states at their surfaces and interfaces. You will seek to understand, and control, the delicate interplay of frustrated triangular and honeycomb lattice geometries, interacting electrons, and effects of strong spin-orbit interactions in stabilising these. Projects are available: (i) utilizing laboratory-, laser-, and synchrotron-based angle-resolved photoemission to probe their intriguing bulk and surface electronic structures and many-body interactions; (ii) developing the epitaxial growth of delafossites by reactive-oxide molecular-beam epitaxy, using a state-of-the-art system recently installed in St Andrews; or (iii) working jointly between us and our research partners at the Max-Planck Institute for the Chemical Physics of Solids, Dresden, pursuing either single-crystal growth of new delafossites, or density-functional theory calculations of their electronic structures, combined with experimental studies in our group. For further information, or to discuss research possibilities, please contact philip.king@st-andrews.ac.uk. As part of this project, you will undertake experiments at national and international facilities. Thus, a willingness to travel is an essential prerequisite.

[1] Kushwaha et al., Science Advances 1 (2015) 1500692
[2] Moll et al., Science 351 (2016) 1061
[3] Ok et al., Phys. Rev. Lett. 111 (2013) 176405
Self-sustained topological phases in quasi-1D and 2D structures
Braunecker, Dr Bernd - bhb@st-andrews.ac.uk

Topological quantum phases have risen to a very active field of research recently, triggered mostly by the realisation that "ordinary" semiconductor nanostructures could be fine tuned to exhibit topological properties which are very attractive for quantum information storing and processing. With the link to semiconductors a major step forward has been taken towards a quantum technological implementation of such states, yet to obtain robust and scalable quantum systems the requirement of fine tuning has to be dropped.

Self-sustained topological phases provide such stable and robust systems, and exhibit a multitude of fascinating new physical properties that emerge as an effect of strongly interacting particles in a condensed matter system. We have already demonstrated that such phases spontaneously appear in hybrid magneto-electronic systems in one dimension [1-4]. Yet in 1D the number of topological states is restricted, and to obtain more exotic topological states extensions to higher dimensions must be made. It is, however, mandatory to maintain then the 1D self-sustaining mechanisms to avoid producing only conventional phases [5].

In this PhD project, we will take a systematic approach towards such self-sustained topological phases by enhancing the complexity of the systems step by step while maintaining full control over the strongly correlated electron state. We will investigate the influence of the lattice structure (square, honeycomb, kagome), anisotropies and frustration, as well as the crucial renormalisation of the system properties by electron interactions.

[1] B. Braunecker, P. Simon, and D. Loss, Phys. Rev. Lett. 102, 116403 (2009) [arXiv:0808.1685]
[2] B. Braunecker, P. Simon, and D. Loss, Phys. Rev. B 80, 165119 (2009) [arXiv:0908.0904]
[3] B. Braunecker and P. Simon, Phys. Rev. Lett. 111, 147202 (2013) [arXiv:1307.2431]
[4] B. Braunecker and P. Simon, Phys. Rev. B 92, 241410(R) (2015) [arXiv:1510.06339]
[5] P. Simon, B. Braunecker, and D. Loss, Phys. Rev. B 77, 045108 (2008) [arXiv:0709.0164]
The effects of non-adiabaticity and noise on quantum state preparation in cold-atom systems
Hooley, Dr Chris - cah19@st-andrews.ac.uk

One of the principal reasons for the current interest in ultracold atomic gases in optical lattices is the possibility they offer to prepare long-lived coherent quantum states 'to order'. This is usually done [1] by a sequence of protocols in which the various lasers creating the optical lattice are 'ramped' from one set of intensities to another, in a certain finite time.
The adiabatic theorem guarantees that, if this is done slowly enough, the system will remain in its ground state. However, in reality there are two problems with this. First, after a certain time - typically a few seconds - three-body collisions start to cause the atoms to escape from the trap. Second, there will inevitably be some noise in the lasers, meaning that the desired intensity as a function of time will not be precisely achieved.

The aim of this project is to deepen the theoretical study of how to optimise the laser ramp profiles for quantum state preparation. Specifically, we shall aim to determine what ramp profiles are optimal in the absence of laser noise, and how strongly the optimal ramp profiles are affected by noise of various sorts. A connection with Berry's transitionless quantum driving [2] presumably also exists; if so, it would be good to explore it.
[1] D. Greif, T. Uehlinger, G. Jotzu, L. Tarruell, and T. Esslinger, Science 340, 1307 (2013).
[2] M.V. Berry, J. Phys. A.: Math. Theor. 42, 365303 (2009)

Category: Theoretical Hard Condensed Matter
Theory of light emission with Berry curvature effects and strong light-matter coupling
Keeling, Dr Jonathan - jmjk@st-andrews.ac.uk

The basic principles of electroluminescence in semiconductors are well understood, but a number of recent experimental developments raise questions that are not fully answered. One example of this concerns transition metal dichalcogenides --- materials that have prompted significant interest due to "opto-spin-valley coupling", meaning that one can selectively excite particular conduction band states with spin polarisation by using the helicity of light. Experimentally, if one drives electrical currents through these devices, one finds circularly polarised light emission [1]. It is known that transport properties are influenced by strong Berry curvature effects leading to an effective magnetic field in momentum space changing signs between the two valleys. However, the effect of Berry curvature in light emission is yet to be explored.

Another example concerns electrically pumped polariton devices [2], where an optically active semiconductor quantum is placed in a microcavity, producing strong coupling between the photon and exciton modes. Some work on theories of this already exists [3,4], but many open questions remain.

The aim of this PhD project is to explore examples such as these, where it is necessary to develop and extend theories of electrical transport and electrical luminescence to understand how to control features such as circular polarisation, and strong matter-light coupling. This project will involve a mixture of analytical and computational work, with a substantial computational component.


This is a joint project with Dr Takashi Oka at the Max Planck Institute (PKS) Dresden. This is intended for students applying to the International Max Planck Research School scheme, which involves a joint programme between St Andrews and Dresden. See http://imprs-cpqm.mpg.de/ for further details

[1] Y. J. Zhang, T. Oka, R. Suzuki, J. T. Ye,, Y. Iwasa. Science 344 6185 (2014)
[2] Schneider et al, Nature 497 348 (2012)
[3] M. H. Szymanska, J. Keeling, and P. Littlewood. Phys. Rev. B 75 195331 (2007)
[4] M. Yamaguchi, K. Kamide, R. Nii, T. Ogawa, and Y. Yamamoto. Phys. Rev. Lett. 111 026404 (2013)
Topological Superconductivity
Mackenzie, Prof Andy - apm9@st-andrews.ac.uk

The concepts of symmetry and symmetry breaking cut across all sub-fields of physics. Whether crystal symmetry in solids, gauge symmetry in superconductors or time reversal symmetry in ferromagnets, we have become used to defining phases of matter in terms of order parameters associated with symmetry breaking. However, not all collective quantum states can be fully characterised in terms of their symmetries. In some systems phases are classified in terms of their topological characteristics. Although this has been known for several decades, it was thought to apply in highly restricted circumstances. Exciting and rapid developments over the past five years have shown that these topologically characterised phases are likely to be much more widespread than first thought, and that, in the long term, it may be possible to exploit their properties in adventurous new technologies. Although progress has been rapid, fascinating theoretical questions remain, not least the interplay between symmetry and topology. The field is also ripe for experimental study. Superconductors are among the most fascinating candidates for topological systems. A host of intriguing theoretical proposals exist, but the extent to which they are observable in practice has yet to be determined. This project is concerned with investigating candidate topological superconductors, using a combination of the world-leading experimental facilities in St Andrews, Dresden and Cornell. The project is ambitious, and would be best suited to a candidate with both experimental and theoretical aptitude.

(Jointly affiliated to both University of St Andrews and Max Planck Institute for the Chemical Physics of Solids, Dresden)
Ultrafast Photophysics of Organic Semiconductors
Samuel, Prof Ifor - idws@st-andrews.ac.uk

This project will explore the physics of remarkable plastic-like semiconductors, such as light-emitting polymers. These materials are model one-dimensional systems and this strongly influences their physics – for example it means that excitons are strongly bound and that there is a substantial distortion of the material when it is excited. The purpose of this project is to study the nature of the excited states in these materials and how they evolve when the sample is excited by light. The initial rearrangement of the molecules occurs on a timescale of 100 femtoseconds. Remarkably we can make measurements on this timescale using advanced femtosecond lasers. We wish to explore how the excited states form and then decay, and how these processes relate to the structure of the material. The results will help understand light emission and amplification, and complementary theoretical work is underway at Heriot-Watt University by Prof. Ian Galbraith.


Photonics

organic semiconductor polariton light emitters
Samuel, Prof Ifor - idws@st-andrews.ac.uk
Turnbull, Prof Graham - gat@st-andrews.ac.uk

When light is confined on the nanoscale it is possible to observe light-matter interactions that are not normally observed in bulk materials. One example is the strong coupling of photons and excitons in wavelength-scale microcavities which leads to a number of unusual phenomena [1,2]. The modes of the cavity couple with the exciton to make a hybrid-light-matter state called a polariton. One can make polaritons lasers that emit coherent light [3] and it has been shown that polaritons can form a Bose-Einstein condenstate [4].

This project will explore the properties of polaritons in microcavities based on organic semiconductors [2,4-6]. It will involve the fabrication of microcavities that include J-aggregate dyes or semiconducting polymers to explore how the energy states of organic materials can be modified when coupled to the cavity modes, and be applied in photonic devices including lasers and LEDs.

[1] C. Weisbuch et al., Phys. Rev. Lett. 69, 3314 (1992)
[2] D.G. Lidzey et al., Nature 395, 53 (1998)
[3] S. Christopoulos et al., Phys. Rev. Lett. 98, 126405 (2007)
[4] J D Plumhof, T Stöferle, L Mai, U Scherf & R F Mahrt, Nature Materials 13, 247–252 (2014)
[5] T. Schwartz, J. A. Hutchison, C. Genet, and T. W. Ebbesen, Phys. Rev. Lett. 106, 196405 –(2011)
[6] S Kéna-Cohen*, S A. Maier and D D. C. Bradley, Advanced Optical Materials 1, 827–833, (2013)
Plastic Lasers
Samuel, Prof Ifor - idws@st-andrews.ac.uk
Turnbull, Prof Graham - gat@st-andrews.ac.uk

Conjugated polymers are a very special class of plastics that are both semiconducting and efficient light-emitters. They have been widely applied as flat and flexible light emitting displays, as well as visible lasers, optical amplifiers, solar cells and electronic circuits. As novel laser media, polymers are particularly attractive because they can be easily and inexpensively formed into flexible shapes and structures that are inaccessible to crystalline materials.

This project builds on our internationally recognised research programme in polymer lasers. We have demonstrated plastic lasers driven by a light-emitting diode and are currently developing lasers and optical amplifiers integrated with nitride LEDs and CMOS control electronics. Novel photonic nanostructures are used to control
laser emission, develop new modes of operation and applications in sensing and datacomms.
Advanced Imaging for the Biomedical Sciences (with Dr F Gunn-Moore, School of Biology)
Cizmar, Dr Tomas - tc51@st-andrews.ac.uk
Dholakia, Prof Kishan - kd1@st-andrews.ac.uk

the aim of this project is to explore new routes for imaging both in vitro and in vivo using concepts of light transmission through disorder. In turn this will allow us to shape light at will for example at the end of an optical fibre and use this perhaps in an endoscopic scenarios. Other forms of microscopy to consider will involve using a light sheet for imaging larger biological systems (eg embryos). The study will involve advanced photonics, numerical studies and practical work. The research will also investigate strategies to image beyond the diffraction limit. Samples under investigation will include tissue and, at later stages of the work, potentially neuronal cells/tissue to target advanced understanding of neurological disease using these methods.
Aligning molecules to improve efficiency in next generation organic LEDs
Gather, Prof Malte - mcg6@st-andrews.ac.uk

Organic light-emitting diodes (OLEDs) are novel type of LEDs in which electroluminescence is generated by plastic-like organic molecules. OLEDs are at the heart of modern smart phone displays and are likely to become the dominant technology for computer screens and large area TVs in the future. In addition, OLEDs are considered for general illumination, an area where efficiency is of key importance. While OLEDs can operate with close to 100% internal electron-to-photon conversion efficiency, typically less than 20-25% of the generated light is extracted into the surrounding air; the rest is trapped in waveguided modes and eventually lost to absorption.

Various strategies have been proposed to improve light extraction from OLEDs. Very recently controlling the average orientation of the electroluminescent molecules inside an OLED has been identified as a promising avenue. However, accurate measurement of molecular orientation is difficult and it remains unclear how molecular orientation can be controlled efficiently. Within this project, these challenges will be approached by making use of different spectroscopic and computational methods. Provided certain formal criteria are met, the student can benefit from placement with a major commercial developer of OLED materials and technology.

Further reading:
Biophysical Aspects of Photodynamic Therapy (Ninewells Hospital, Dundee)
Brown, Dr Tom - ctab@st-andrews.ac.uk
Wood, Dr Kenny - kw25@st-andrews.ac.uk

Photodynamic Therapy (PDT) is a treatment for cancer that involves light-activation of a photosensitiser and causes cell death by release of singlet oxygen and free radicals. The Scottish PDT Centre was established in Ninewells Hospital, Dundee in 2000 thanks to a generous donation from the Barbara Stewart Charitable Trust. Since its introduction in Dundee, over 2,000 treatments have been carried out. The photosensiters used for PDT also have the property that they fluoresce and so they can be used for photodiagnosis (PD), which is performed at the Scottish PDT Centre to direct the surgeon towards tissue that is likely to be cancerous.
The purpose of the proposed PhD program is to gain a fuller understanding of the interaction between the incident light and the tumour. Optimal treatment regimes have not been established. We would like to be able to model both PDT and PD. To assist in this, we propose to develop theoretical radiation transfer models using Monte Carlo techniques in order to simulate the incident light and the fluorescent emission. This will be done for the range of tissue types where PDT is performed in Dundee. This includes skin (the most accessible), the oral cavity, the brain and bladder.
The work will also find application in a wide range of other areas in the drive towards minimally invasive and highly targeted therapies. In addition to the PDT described above, the techniques can be applied to so-called ‘caged compounds’ that are a range of biologically active compounds that are activated with light. In order to apply such compounds within a therapeutic environment, understanding the light tissue interactions is of key importance.
Light distribution measurements will be made around a range of light delivery devices, including cylindrical diffusers and miniature balloons filled with light-scattering media. Further measurements will be carried out using optical fibres embedded in tissue samples and using ultrashort pulses to probe two-photon activation at depth within the body. Fluorescent emission spectra will also be measured using a specially constructed optical biopsy system.

This project provides many opportunities for the student to study PDT and other light activated therapies from theoretical, experimental, and clinical perspectives.
There will be joint supervision from Dr Harry Moseley, who is Technical & Scientific Director of the Scottish PDT Centre and Honorary Reader at the University of Dundee, and Drs Tom Brown and Kenny Wood, who are Lecturers in the Department of Physics and Astronomy at the University of St Andrews. Dr Wood will supervise the theoretical aspects of the PhD (Monte Carlo radiation transfer), Dr Brown the experimental light tissue studies and Dr Moseley will supervise the clinical applications at Ninewells Hospital.

Harnessing Quantum Mechanics to Create Improved Solar Cells
Lovett, Dr Brendon - bwl4@st-andrews.ac.uk

The operation of a modern design of a solar cell consists of three stages: light absorption, movement of electronic excitation, and charge separation. We recently showed that the rate of the first of these, light absorption, can be markedly improved in a symmetric ring of molecules by exploiting quantum interference [1]. In this project you will consider both light absorption and exciton transport, and probe the extent to which quantum mechanical models can be used to improve the operation of solar cells. You will go beyond idealised designs to look at realistic quantum systems. You will focus on systems that are available for immediate testing in the laboratories of collaborators - for example, semiconductor quantum dots or organic molecules.


You will work to understand how these systems interact with their environments, and model the combination as open quantum systems. This will be done using a variety of simple and more sophisticated techniques, as it becomes clear which approximations can be made. The final aim of the project will be to propose an experiment in which a clear signature of enhanced light absorption could be seen.


[1] Superabsorption of light via quantum engineering, K. D. B. Higgins, S. C. Benjamin, T. M. Stace, G. J. Milburn, B. W. Lovett and E. M. Gauger, Nature Communications 5 4705 (2014)


Hawking radiation in the laboratory
Koenig, Dr Frieder - fewk@st-andrews.ac.uk

Black holes can be understood in a simple picture: Imagine a river flowing towards a waterfall with ever increasing flow speed. Also imagine fishes in the river swimming upstream. At some position in the river the maximum speed of the fish will equal the flow speed and all fish beyond that "point of no return" will be flushed into the waterfall. Here the flow speed corresponds to the gravity of a black hole and the point of no return to the event horizon.
Arguably the most facinating aspects of astronomical black holes is the emission of Hawking radiation from the event horizon, an intriguing quantum effect combining gravity, thermodynamics and quantum mechanics.

Unfortunately, the astrophysical Hawking radiation is far too weak to ever being detected directly. Recently, however, we have invented a method to create moving artificial event horizons with short pulses in optical fibers. Moreover, the expected Hawking radiation is strong enough to be detectable with single photon coincindence counting.

The idea of the PhD programme is the calculation, detection, and characterization of this elusive Hawking radiation for the first time. The work has already gained momentum in our group and a setup is built using optical pulses of just a few cycles pulse length. In addition we will explore similar quantum effects such as the Unruh effect and the dynamical Casimir effect.
Integrated Magnetic Resonance Doctoral Training Centre
Smith, Dr Graham - gms@st-andrews.ac.uk

The new EPSRC Doctoral Training Centre in Integrated Magnetic Resonance is a collaboration between 6 of the UK's leading Universities in Advanced Magnetic Resonance Instrumentation and Techniques and includes St. Andrews, Dundee, Aberdeen, Warwick, Nottingham and Southampton.

The aim is to provide a coherent training program for doctoral students whilst working on new research topics in instrumentation and methodology, associated with Magnetic Resonance Imaging, Electron Magnetic Resonance, Nuclear Magnetic Resonance and Dynamic Nuclear Polarisation (which collectively represent £multi-Billion annual markets). Training is delivered from all centres, through residential workshops and over the Access Grid, primarily in the first two years of study.

Funded 4 year PhDs include fees and maintenance of £14000 (tax free) per annum as well as an enhanced travel budget. All PhDs will have internal and external mentors from other centres.

At St Andrews, PhD projects are available on themes associated with major advances in Electron Magnetic Resonance and Dynamic Nuclear Polarisation and are likely to involve collaborations with other centres and other interdisciplinary groups.

PhD topics are likely to involve a combination of instrumental, methodological and computational techniques that would normally be associated with Basic Technology programs.

Representative PhDs from all 6 centres are listed on www.imr-cdt.ac.uk, but other PhD topics may be available on request.

For PhDs at St Andrews, applications can be made directly to St Andrews or via Warwick where the DTC program is administered.

Light harvesting networks
Lovett, Dr Brendon - bwl4@st-andrews.ac.uk

Recent ultrafast optical experiments on photosynthetic complexes reveal the possible presence of quantum coherence between excitations on different parts of the protein complexes involved. It has been conjectured that these quantum correlations may lead to enhanced energy transfer, and thus to more efficient solar cells.

In this project, you will explore the interplay of quantum and classical mechanisms for moving electronic energy around networks of molecules. On the one hand, quantum correlations can lead to constructive interference between different parts of the network, leading to a faster transport of energy. On the other hand, such correlations may lead to destructive interference, and cause excitations to get stuck. Classical hopping may relieve this problem. You will predict the optimal balance of classical and quantum processes that lead to the highest rate of energy extraction from the network. You may need to explore the role of length scale, network topology, and use thermodynamic concepts to address this problem.

The project will be in collaboration with theorists at the University of Oxford, and may be tested in the laboratories of collaborators both in St Andrews, and at the Universities of Oxford and Cambridge.
Linear and nonlinear properties of 3D optical Metamaterials.
Di Falco, Dr Andrea - adf10@st-andrews.ac.uk

Metamaterials (MMs) are man made materials with engineered optical properties. They are made assembling their artificial atoms at a scales much smaller than that of light, so as to appear homogenous. They are at the basis of very thought provoking proposals, including super imaging and cloaking applications.
In the group of Synthetic Optics we have developed a large portfolio of fabrication techniques for one- and two-dimensional MMs.

The aim of this project is to develop the fabrication protocol and applications of three-dimensional MMs obtained with a bottom up approach. The student will combine the extraordinary physical and optical properties of silica based aerogels with the flexibility of the design of nanoplasmonics to realise effective materials with bespoke optical behaviour. The aerogel is an ultra light material with refractive index close to unity and thermally more insulating than air. Combining these features with the field enhancement offered by infiltrated metallic nano particles is specially suited to address nonlinear effects at ultra-low powers.

This challenging but rewarding project requires a thorough understanding of the physics involved and the experimental rigour to fabricate and test the MMs, but offers the student the chance to learn a broad range of design, fabrication and experimental techniques.

Living Lasers: Lasing from biological cells
Gather, Prof Malte - mcg6@st-andrews.ac.uk

Optical phenomena in biological structures have fascinated mankind for centuries and biological materials with optical functionality are currently a major topic of research. In the future, photonic devices may indeed be based on natural or genetically engineered optical function.

Recently, we developed a biological laser – a device based on a single living cell genetically programmed to produce the fluorescent protein GFP. The laser is biocompatible and biodegradable, and thus offers unique physical and biological properties not shared by any existing device.

However, so far our biolasers require an artificial resonator and an external pump source. This project is aimed at gaining a better understanding of lasing and stimulated emission in biological materials and at developing new avenues to biolasers. For example, this can include the study of bio-assembled resonators based on naturally occurring structures, photophysical investigations aimed explaining why fluorescent proteins are such efficient laser materials, or the development of biocompatible nanolasers.

The project is inter-disciplinary, involving photonics, laser physics, genetic engineering, proteomics, and material science and adequate training in these fields will be provided within the school and through external collaborators.

Further reading
Measuring nanometre distances with EPR to investigate the structure of biomolecules
Lovett, Dr Janet - jel20@st-andrews.ac.uk

Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool capable of measuring accurate nanometre-scale distances between radical centres. You will utilise this capability for studying a range of molecules of biological interest from the structure of RNA using novel labelling techniques to the structure of protein complexes such as the SecA:SecYEG translocon of Gram negative bacteria, binding partners of calmodulin (including nitric oxide synthase), C3 and myosin. You will be at the forefront of the technique by not only applying it to measure important systems but also driving the boundaries in terms of information that can be gained from a single measurement, the radical centres that can be used and the physical conditions (such as temperature-at the moment most measurements are carried out at 50 kelvin) that are necessary for good measurements.

You will use the outstanding EPR equipment in St Andrews which includes a high power X/Q band and a home-built world-leading W-band spectrometer.

In addition you will help prepare samples in specialist laboratories in the Biological and Medical Sciences building and in Chemistry.

Project partners include Professor I. Collinson (Bristol), Dr M. Pfuhl (KC London), Dr E. Anderson (Oxford), Professor D. Evans (Warwick), Dr S. Daff (Edinburgh), Professor P. Barlow (Edinburgh), Professor N. Scrutton (Manchester), Dr A. Hulme (Edinburgh), Dr G. Smith (St Andrews) and Dr D. Norman (Dundee).

You will therefore receive a thorough training in spectroscopic techniques and biological sample preparation.

Your background should be in the Physical or Biological Sciences and you should have an interest in learning a wide range of methods.

The funding is competitive so you must have (or be predicted) a good degree.

Informal enquiries welcome.

Funding is appropriate for those with residential status in the UK (though exceptions may be possible) and will be for 3.5 years.

URL: https://risweb.st-andrews.ac.uk/portal/da/persons/janet-eleanor-lovett%28669e4b4e-e06b-41da-9737-08d697b5bb85%29.html
MM-wave Radar, Components and Techniques
Smith, Dr Graham - gms@st-andrews.ac.uk

MM-waves represent the area of the electromagnetic spectrum that sits between microwaves and Terahertz frequencies. It is the part of the spectrum where electronics meets optics and a wide variety of physical techniques are used to design components and systems. MM-waves are used in high resolution radar, fusion diagnostics, earth resource studies, magnetic resonance and security systems.

The mm-wave group at St Andrews is one of the largest and most well established groups in this field in the UK, and has a strong track record in designing components, sub-systems and full system. Much recent work ahas concentrated on developing radar imaging systems for earth resource studies (imaging volcanos, monitoring rainfall) and for various security related systems.
There is also a very strong program in mm-wave magnetic resonance.

A variety of PhD topics are always available and any interested student should get in touch with Dr Graham Smith in the first instance.
New photonics tools unravel the mysteries and mechanics of biological cells
Gather, Prof Malte - mcg6@st-andrews.ac.uk

Biologists have compelling evidence that in addition to biochemical signals, mechanical forces have a major impact on a wide range of processes in cell biology, with examples ranging from cell migration and cell growth to the spreading of cancer and the differentiation of stem cells. However, there is at present a shortage of suitable tools to measure the force exerted by a cell which often is well below 1nN (i.e., < 10-6 N (!)).

By developing a novel optical micro-cavity-based sensor technology, the Gather Lab seeks to overcome current limitations in measuring cellular forces and – for instance – investigate the mechanics involved in the formation and the growth and repair of nerve cells.

The basic working principle of our sensors is to detect shifts in the resonance frequency of a micro-cavity due to mechanical forces applied by cells cultured on the sensor. These shifts can be detected with high spatial and temporal resolution and the forces at play are then computed from this by a finite element method.

A PhD in the field of cellular mechanics provides you with a broad, interdisciplinary skill set: You will learn and apply a range of micro- and nano-fabrication methods and work in a state-of-the-art cleanroom. You will use different types of optical spectroscopy and work with atomic force microcopy. You will receive hands-on training in cell culturing techniques and perform studies of e.g. stem cell differentiation.

The project is part of an international collaboration with leading scientists at Harvard Medical School and University of Cambridge which is funded by the Human Frontier Science Program, the leading funding institution for interdisciplinary and international collaborative research into complex biological systems.

 
New radical probes for cysteine rich proteins
Lovett, Dr Janet - jel20@st-andrews.ac.uk

Electron paramagnetic resonance (EPR) spectroscopy is proving to be a very useful tool for investigating protein structure via nanometre distance measurements. In order to make these measurements proteins are often labelled with small radical-containing molecules at available cysteines.

However, many proteins contain too many cysteines already to make this approach viable. You will design and synthesise new labels suitable for cysteine-rich proteins and characterise their EPR properties once bound to proteins. This is a new project and will offer you the chance to be at the forefront of an emerging field. The work will be carried out jointly in the Schools of Chemistry and Physics & Astronomy using state-of-the art facilities and equipment for synthesis and EPR spectroscopy.

Relevant reading:

G. Jeschke Annu. Rev. Phys. Chem. 63 419 (2012)
J. E. Lovett et al Phys. Chem. Chem. Phys. 11 6840 (2009)
G. W. Reginsson et al J. Magnetic Resonance 216 175 (2012)
M. R. Fleissner et al Proc. Natl. Acad. Sci. 106 21637 (2009)
M. R. Fleissner et al Proc. Natl. Acad. Sci. 108 16241 (2011)

Funding is appropriate for those with residential status in the UK (though exceptions are possible) and will be for 3.5 years.
Nonlinear Optical Micromanipulation
Dholakia, Prof Kishan - kd1@st-andrews.ac.uk

New uses of trapped colloid as nonlinear media and uses for observations of soliton-like waves and new forms of in-situ imaging as well as nonlinear processes (eg 4 wave mixing). This is a very exciting project based on novel ordering of colloidal particles in the presence of light fields as well as the use of these colloids as new media for nonlinear effects.
OLED micro-displays as biophotonic platform
Gather, Prof Malte - mcg6@st-andrews.ac.uk

Organic Light Emitting Diodes (OLEDs) are novel optoelectronic devices with potential applications ranging from displays (e. g. in smart phones or for flexible screens) to general illumination. In contrast to conventional LEDs, OLEDs are based on plastic-like organic materials. Thus, they can be mechanically flexible and are believed to offer improved biocompatibility.

In this project, micro-displays based on >200,000 individual OLEDs, each smaller than a single biological cell, are used as a platform for advanced studies in cell biology. Potential applications include lens-free, low-cost, continuous microscopy of cells and structured illumination for optogenetic studies. Optogenetics is a technique which allows controlling the biological activity of genetically modified cells by exposure to light. Over the past decade, the technique has greatly improved the understanding of various fundamental processes in biology, in particular in neuroscience. OLED micro-displays may enable optogenetic experiments, like stimulating growth or movement of neurons, with improved temporal and spatial control, higher degree of parallelization and over longer times than currently possible.

This project is highly interdisciplinary involving photonics and materials science but also cell biology and genetics. Training will be provided in all these aspects from within my group and through collaboration with the School of Biology and external collaborators at University of Cambridge and Harvard Medical School.

Further reading:
optical antennas for visible light communications (Li-Fi)
Samuel, Prof Ifor - idws@st-andrews.ac.uk
Turnbull, Prof Graham - gat@st-andrews.ac.uk

Visible light communications is an emerging field that aims to deliver high-bandwidth wireless data through solid-state (LED) lighting. This project will be part of a multi-disciplinary research collaboration between the Universities of St Andrews, Strathclyde, Edinburgh, Oxford and Cambridge which will develop the next generation VLC technology.

The aim of this project will be to develop nanophotonic hybrid light sources and detectors based on luminescent polymer films. The student will design novel optical antennas, and fabricate these using thin film depostion and nanoimprint lithography. Working with the partner universities, these components will be combined with gallium nitride LEDs and CMOS detectors to develop next generation tranceiver technologies for visible light communications.
Optical excitation of new drugs
Brown, Dr Tom - ctab@st-andrews.ac.uk

Caged compounds are biologically active molecules that have had their functionality blocked by the addition of a chemical group. A flash of light at the right wavelength removes this caging group switching on the functionality of the drug. Working closely with collaborators in Oxford we are exploring how we can combine advanced photonic techniques with the action of these drugs to permit, for example different colours to activate different drugs in the same system. We would also like to explore the interaction of short pulses with these drugs to further enhance the possibility of their activation in experimental systems, and ultimately within living tissue. AT this stage some of our research is focussed on the application of these techniques to problems in neuroscience including initial attempts at better understanding the physical basis of memory.
Optical manipulation: air/vacuum trapping for cavity optomechanics
Dholakia, Prof Kishan - kd1@st-andrews.ac.uk

Optical trapping leads to the confinement of microscopic and nanoscopic objects using light. In the domain of optomechanics we would like to cool small "trapped" mechanical oscillators down to the quantum regime. This project aims to experimentally explore new ways to levitate and trap microparticles in air and vacuum. The ultimate aim is to slow down or 'cool' spheres to the ground state of motion. The topic is currently one of the most exciting and rapidly growing areas of physics and will involve both theory and experiment.
Organic light-emitting diodes
Samuel, Prof Ifor - idws@st-andrews.ac.uk

Visible light emission can be stimulated by applying a voltage to a thin layer of an organic semiconductor. The light emitted provides a window on the physics of the material, enabling us to learn about the nature of the excited states in the material. It is also useful for information display, lighting, and even for the treatment of skin cancer. We have developed a new class of light-emitting organic semiconductor, which could be used for high efficiency lighting, thereby reducing energy consumption.
Organic Solar Cells
Samuel, Prof Ifor - idws@st-andrews.ac.uk

The energy crisis is probably the most important problem facing the world today. Sunlight is the most abundant renewable energy source, but at present the cost of photovoltaics is too high for solar cells to be a serious alternative to fossil fuels. Organic semiconductors offer the prospect of low cost solar cells, but their efficiency needs improvement. We are working on new measurements to understand organic solar cell operation, and new materials to improve it.
Radical approaches for investigating the structure of nitric oxide synthase
Lovett, Dr Janet - jel20@st-andrews.ac.uk

Nitric oxide synthase (NOS) is found in several isoforms throughout the human body. It synthesises nitric oxide from arginine for signalling but it must be tightly regulated - increased turnover of NOS is detrimental to health and for example is implicated in causing major damage after an ischemic stroke.

NOS is a 160 KDa protein which is found as a homodimer. It consists of a heme and pterin containing oxygenase domain and a FMN, FAD and NADPH-binding reductase. For function NOS binds calmodulin.

Despite its interest, the structure of the NOS homodimer is not fully known and neither are the conformational changes that must occur during activity.

One possible method for investigating these structural questions in NOS is to use electron paramagnetic spectroscopy (EPR) to measure nanometre-scale distances between pairs of radical centres. These radicals may be intrinsic (i.e. the cofactors) or extrinsic stable radical-containing species called spin labels.

Spin labels are traditionally bound to cysteine amino acids but NOS contains 30 free cysteines and thus new approaches will be developed with the aid of a synthetic chemistry post-doc linked to this project.

This ambitious work will involve over-expressing NOS and its domains and preparing samples for EPR with either intrinsic radicals or spin labels, as well as measuring with EPR and analysing results. You will therefore have the opportunity to work across Biology, Chemistry and Physics at the University of St Andrews. The EPR grouping at St Andrews and Dundee is excellent with a wide range of expertise and state-of-the-art instruments.

Your background could be either in biochemistry/medicine, chemistry or physics so long as you have an interest in learning a range of techniques and preparing protein samples.

The funding is competitive so you must have a good degree.

Informal enquiries welcome.

Funding is appropriate for those with residential status in the UK (though exceptions may be possible) and will be for 3.5 years.

References:
G. Jeschke Annu. Rev. Phys. Chem. 63 419 (2012)
S. Daff Nitric Oxide 23 1 (2010)
Redefining optical resolution limit
Mazilu, Dr Michael - mm17@st-andrews.ac.uk

Classically, Abbe’s relation on diffraction gives the optical resolution limit. This means that every imaging device, such as a microscope, will not be able to resolve features smaller then this limit. Physically, this limit is defined by the area of the diffraction pattern (Airy disk) of a circular aperture illuminated by a plane wave. Recently, multiple methods have been proposed to focus light and image with resolutions beyond this limit. This project will look at a redefinition of the 140 years old optical resolution limit. The project is theoretical in nature where the beams are numerically modelled to determining their resolving powers. Ultimately, the questions we want to answer are: What is the optical resolution limit of a given optical setup? How is this limit extended when including non-linear effects? What is the role of structured illumination and structured detection in defining this limit?
Single Molecule Spectroscopy of Semiconducting Polymers
Penedo-Esteiro, Dr Carlos - jcp10@st-andrews.ac.uk
Samuel, Prof Ifor - idws@st-andrews.ac.uk

This project combines two rapidly advancing fields of physics. One is the field of “plastic” semiconductors which are of interest for light-emitting diodes, solar cells and lasers. The other is single molecule spectroscopy in which light emission from a single molecule is studied. The aim of the project is to perform single-molecule measurements on semiconducting polymers in order to gain new insight into the light-emission process, and how it relates to the structure of the material. Single-molecule spectroscopy is particularly powerful for doing this because it enables the differences between individual molecules to be observed, whereas most measurements just average over many molecules. The project aims to observe and manipulate the structure and light-emission of individual polymer molecules in real time. This is in turn will lead to new understanding of how their properties relate to their structure that could lead to improved optoelectronic devices.

Single-molecule TIRF and FCS spectroscopy of protein-lipid interactions involved in Alzheimer's disease
Penedo-Esteiro, Dr Carlos - jcp10@st-andrews.ac.uk
Samuel, Prof Ifor - idws@st-andrews.ac.uk

The ability of proteins, nucleic acids and lipid molecules to assembly in a variety of structures underpins of life processes. However, under cellular stress, some of these biomolecules organize into structures not only unable to perform their biological function but in fact into toxic species with severe consequences in human health. In this context, the aggregation of the amyloid peptide is a hallmark of Alzheimer’s disease and has become a model system for the study of toxic aggregation pathways [1,2].
In this project, we aim to develop and apply specifically tailored wide-field total internal reflection (TIR)[3] and fluorescence correlation single-molecule fluorescence imaging methods (FCS)[4] to investigate amyloid structure and dynamics in the presence of artificial lipid vesicles and supported lipid bilayers as models of the cellular membrane. The combination of both single-molecule approaches is particularly powerful as enables to interrogate the aggregation mechanism with temporal resolutions from microseconds to seconds in freely diffusing samples (Fluorescence Correlation Spectroscopy) and from milliseconds to minutes and even hours using surface-immobilized techniques (wide-field TIR). In collaboration with Prof. Ifor Samuel, also in the School of Physics, we will investigate the interaction of fluorescently labelled amyloid aggregates and other neurologically relevant proteins with lipid membranes at single-molecule level using protocols already developed in our team.

References
1. Eisenberg D, Jucker M (2012) The amyloid state of proteins in human disease. Cell, 148: 1188-1203.
2. Miller Y, Ma B, Nussinov R (2010) Polymorphism in Alzheimer amyloid organization reflects conformational selection in a rugged energy landscape. Chem. Rev. 110: 4820-4838.
3. Roy, R. et al (2008) A practical guide to single molecule FRET. Nature Methods 5(6): 506
4. Haustein, E., Schwille, P. (2007) Fluorescence correlation spectroscopy: novel variations of a established technique. Ann. Rev. Biophys. Biomol. Struct. 36: 151
The development and control of ultrafast lasers
Brown, Dr Tom - ctab@st-andrews.ac.uk

Ultrafast lasers are a class of devices that emit pulses in the fs regime. These lasers are now used in a wide range of applications from eye surgery to materials processing. Many such devices are based on techniques that were developed in St Andrews about 20 years ago. There still remain significant challenges with these systems including reducing cost and complexity, accurately measuring and understanding the output from these lasers and providing mechanisms for remote operation. In this project you will be working with the ultrafast laser group developing new materials and technique. You would also be expected to work closely with applications users to ensure that sources are developed which solve real world problems.
The optical characterisation of tissue samples (in conjunction with Professor Simon Herrington, School of Medicine)
Brown, Dr Tom - ctab@st-andrews.ac.uk

The use of tissue samples underpins much working medical diagnosis. For example patients regularly undergo tests where tissue samples are taken and subsequently examined by a pathologist. In this project we seek to show that advanced techniques such as Raman spectroscopy may be used to provide additional support to the pathologist in making accurate diagnosis by examining the underlying biochemistry of the sample. A project in this area will involve working closely with our researchers in Raman spectroscopy as well as with clinical staff from the School of Medicine. Students will build and run advanced spectroscopy system and play an active role in the statistical analysis of their results.
Waveguide lasers
Brown, Dr Tom - ctab@st-andrews.ac.uk

Most solid-state lasers require bulky and complex cavities. In this project we will explore how, by using optical confinement within a gain medium laser performance can be greatly enhanced. In it’s simplest form this comprises a one-dimensional confinement, however we also wish to explore the operation of channel waveguide devices based on either micro-machined or femtosecond direct written structures. Ultimately with mirrors attached directly to the endfaces of such devices, fully monolithic cavities can be produced. The geometry of such devices also permits intriguing opportunities for innovative pumping designs ultimately allowing the generation of high power output. Our vision is to incorporate technologies that permit the generation of ultrashort pulses for these devices and show, with the help of our collaborators, a wide range of applications for these lasers.