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

Galactic Dark Matter Effects from New Physics of Modified Gravity or Dark Energy
Zhao, Dr Hongsheng - hz4@st-andrews.ac.uk

We explore alternatives to the Cold Dark Matter framework by adding new physics in Dark Matter.
The new physics could include Modified Gravity or matter with fifth force interactions.
Several rare coincidences of scales in standard particle physics
are needed to explain why the negative pressure of the cosmological dark energy (DE)
(i) coincides with the positive pressure of random motion of dark matter (DM) in bright galaxies,
(ii) is within order of magnitude of the energy density of neutrinos, if it is allowed to have a mass of eV.
(iii) why Dark Matter in galaxies seems to follow the Tully-Fisher-Milgrom (MOND) relation of galaxy rotation curves, rather than the CDM predicted profile.
The aim is to link empirical dark matter constraints in galaxies with the cosmology.
The work can be purely theoretical using the Euler-Lagrangian approach. Or empirical by fitting galaxy velocity distributions and Gravitational Lensing data.
3D atmosphere simulations of giant gas planets and mini-Neptunes
Helling, Dr Christiane - ch80@st-andrews.ac.uk

Extrasolar planets have proven to be far more diverse than the planets in the solar system. This project will study the climate of giant planets and mini-Neptunes by conducting 3D global circulation simulations.

Giant gas planets and mini-Neptuns form in the outer, most cool parts of planet forming disks but end up with different masses. How does this effect their climate? How does the climate change depending on their orbital position? How can this be observed?

This project will focus on the 3D climate simulations that self-consistently include cloud formation in chemically different environments. The aim of the project is to compare the 3D atmospheric structures of mini-Neptuns with the well-studied case of giant gas planets (e.g. HD189733b). The project will also study ionisation processes in exoplanet atmospheres that may lead to the formation of an ionosphere and the occurrence of lighting. Lightning may provide a new window into the dynamic atmospheres of extrasolar planets which so far is observed as an unresolved dot in the sky. This project is timely linked to the launch of JWST, the largest IR and near-IR space telescope in years to come.


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

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.

By treating galaxies as independent entities to determine their physical properties, we are missing vital information. A better approach would be to treat them as a population of objects with common origin. This could tighten constraints on physical properties of galaxies, but also mean that we can extract more useful information from large surveys producing lower quality observations.

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. 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. This project would suit students with a background in astrophysics but aptitude for maths and statistics, and also those with a background in maths, statistics or physics and interest in astrophysics.

Please contact Vivienne Wild, the lead supervisor for the project, for more information (vw8@st-andrews.ac.uk). This project will be co-supervised by Dr Rita Tojeiro.

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.
Dissecting galaxies in transition
Wild, Dr Vivienne - vw8@st-andrews.ac.uk

The number density of `red and dead' elliptical galaxies increases with cosmic time, meaning galaxies must be transitioning from star-forming disks. In this project we will use the SDSS-IV MaNGA integral field survey alongside mock observations of hydrodynamic simulations to move beyond demographics and pin down which physical processes are responsible for this transition, as a function of stellar mass and environment.

Massive galaxies in the nearby Universe typically fall into two distinct populations (e.g. Strateva et al. 2001; Baldry et al. 2004): actively star-forming disk galaxies, and `red and dead' elliptical galaxies with little or no signs of ongoing star formation. The bimodality in the star-forming properties of massive galaxies has existed since at least z~2 (Tomczak et al. 2014), and the strong correlation between star-forming properties and morphology holds to a similar epoch.

The increasing number density of red-sequence galaxies with cosmic time at fixed stellar mass (e.g. Moutard et al. 2016) tells us that galaxies move from the blue-cloud to the red-sequence by having their star formation halted (`quenched'). Coincidentally, the typical star formation rate of galaxies decreases as they exhaust their gas supplies, but this process is unable to account for the alteration in the galaxies' morphologies. Many different mechanisms have been proposed to partly or wholly explain the build-up of the quenched elliptical population with time, such as gas stripping, merger induced starbursts, AGN feedback and morphological quenching.

Catching galaxies that are in the act of transition, and studying both their evolving demographics and their properties in detail, alongside mock observations from state-of-the-art simulations, are the ways to make further progress (Wild et al. 2009). These objects are rare, and only recently have surveys been large enough for us to be able to constrain the number density evolution of green-valley and post-starburst galaxies, alongside the quiescent galaxies we expect them to evolve into.

The advent of highly multiplexed integral field surveys, alongside well developed hydrodynamic galaxy simulations, means the time is perfect for a fully encompassing study of all types of candidate-transition galaxies. The fossil record of a galaxy's formation history is encoded in its morphology, stellar kinematics, stellar populations and dust, ionised gas content and kinematics. The MaNGA survey provides access to all of these, alongside robust control samples, volume correctable number densities, a wide range of environments and stellar masses. Importantly, comparison to large numbers of hydrodynamic simulations is now possible, converted into mock data cubes to be analysed in exactly the same way as the data.

In this project we will study the morphologies, shapes, spatially resolved kinematics and stellar populations of the largest ever sample of local post-starburst, blue-ellipticals, red-spirals and green-valley galaxies observed with an integral field unit, alongside large sets of control samples and hydrodynamic simulations. We will aim to understand what are their ancestors and descendants and thereby understand whether they are truly transitioning populations, and on what timescales. We will use these results to interpret data from high-redshift surveys, where post-starburst galaxies are far more common and potentially important for building the present-day galaxy bimodality (Wild et al. 2016).

This project will be co-supervised with Dr Anne-Marie Weijmans, lead observer for MaNGA.

Strateva et al. 2001, AJ 122, 1861
Baldry et al. 2004, ApJ 600, 681
Tomczak et al. 2014, ApJ, 783, 85
Moutard et al. 2016, A&A, 590, 103
Wild et al. 2009, MNRAS, 395, 144
Wild et al. 2016, MNRAS, 463, 832
MaNGA survey : http://www.sdss.org/surveys/manga/
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.
Irradiated brown dwarfs in the galaxy
Helling, Dr Christiane - ch80@st-andrews.ac.uk

Brown dwarfs are very low-mass stars which are as cool as planets. In contrast to planets, most of the brown dwarfs are fast rotators with strong magnetic fields causing strong radio emission to emerge. The origin of this radio emission is largely unsolved but must be linked to the atmospheric environment somehow. This project therefore focuses on the 3D structure of brown dwarf atmospheres under the effect of external irradiation. External irradiation will ionise the upper atmosphere but also affect the energy budget of the underlying and cloud forming atmospheric regions.

The aim of this project is to develop a 3D climate model for brown dwarfs under the effect of external irradiation in order to study for the first time the interior of a 3D brown dwarf atmosphere as well as the possibility of the emergence of a chromosphere environment. First, we will study a generic set up, but will apply this model to white dwarf - brown dwarf binaries and free-floating brown dwarfs in different galactic environments.
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.
New physics for Dark Matter via Modified Gravity/Dark Energy

We explore alternatives to the Cold Dark Matter framework by adding new physics in Dark Matter.
The new physics could include Modified Gravity or matter with fifth force interactions.
Several rare coincidences of scales in standard particle physics
are needed to explain why the negative pressure of the cosmological dark energy (DE)
(i) coincides with the positive pressure of random motion of dark matter (DM) in bright galaxies,
(ii) is within order of magnitude of the energy density of neutrinos, if it is allowed to have a mass of eV.
(iii) why Dark Matter in galaxies seems to follow the Tully-Fisher-Milgrom (MOND) relation of galaxy rotation curves, rather than the CDM predicted profile.

The work can be purely theoretical using the Euler-Lagrangian approach. Or empirical by fitting galaxy velocity distributions and Gravitational Lensing data.
New Physics for Galactic Dark Matter via Modified Gravity/Dark Energy

We explore alternatives to the Cold Dark Matter framework by adding new physics in Dark Matter.
The new physics could include Modified Gravity or matter with fifth force interactions.
Several rare coincidences of scales in standard particle physics
are needed to explain why the negative pressure of the cosmological dark energy (DE)
(i) coincides with the positive pressure of random motion of dark matter (DM) in bright galaxies,
(ii) is within order of magnitude of the energy density of neutrinos, if it is allowed to have a mass of eV.
(iii) why Dark Matter in galaxies seems to follow the Tully-Fisher-Milgrom (MOND) relation of galaxy rotation curves, rather than the CDM predicted profile.

The work can be purely theoretical using the Euler-Lagrangian approach. Or empirical by fitting galaxy velocity distributions and Gravitational Lensing data.
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.
Understanding the impact of structure formation on galaxy evolution using DESI
Tojeiro, Dr Rita - rmftr@st-andrews.ac.uk

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, particularly of 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 the star formation history, chemical enrichment and dust content of galaxies, we will be able to link the evolution of galaxies with their cosmological and local environment with unmatched 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. You will use simulations to understand how complex star-formation histories might be able to be simplified and parametrised (e.g. Diemer et al. 2017).

You will then be able to study the detailed evolution of galaxies within the intricate context of their large- and small-scale environment, which will be beautifully characterised by DESI - see Tojeiro et al. 2017 for an example on GAMA data.

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

This project will be co-supervised by Dr Vivienne Wild.

References:
The DESI survey: https://arxiv.org/abs/1611.00036v1
Montero-Dorta et al. 2016, MNRAS, 461, 1131
Diemer et al. 2017, ApJ, 839, 26
Tojeiro et al. 2017, MNRAS, 470, 3720
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

Coexistence or Competition: Resolving the phase diagram of unconventional superconductors through atomic scale imaging of emergent phases
Wahl, Prof 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 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 establish an 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).
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.
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, Prof 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, Prof 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 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 material systems 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 starting to be explored. 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 [e.g. 1-4], 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] Riley et al., Nature Physics 10 (2014) 835
[2] Riley et al., Nature Nano. 10 (2015) 1043
[3] Bawden et al., Nature Commun. 7 (2015) 11711
[4] Bahramy, Clark et al., Nature Materials, in press (arXiv:1702.08177) (2017)
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, Prof Phil - pdk6@st-andrews.ac.uk
Wahl, Prof 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).
Artificial Quantum Materials - Thermodynamics And Transport
Rost, Dr Andreas - ar35@st-andrews.ac.uk

Artificial designer heterostructures of correlated electron systems open up a wide range of exciting possibilities for the creation of new materials. The atomic-layer-by-atomic-layer deposition now achievable in thin films gives a unique potential to manipulate the properties of this still poorly explored new class of materials, ultimately allowing the creation of new phases with properties difficult to attain in bulk compounds [1]. St Andrews has recently opened a new dedicated MBE growth facility with the aim of exploiting the possibilities of such tailored materials.

This new class of materials, however, poses a key challenge to experimentalists interested in such basic thermodynamic properties as specific heat and magnetisation. The extremely low ‘thermal mass’ of such materials compared to bulk systems ultimately requires the development of a new bespoke set of experimental tools for measurement. To bring the paradigm of such fundamental thermodynamic measurements to nanoscale thin films is the key aim of a new research program established at the University of St Andrews of which you will be a key member. During your PhD you will contribute to the development of these new tools with the aim to applying them to the study of designer quantum materials spanning phenomena such as superconductivity, novel (topological) Dirac- and Weyl- systems and (quantum) spin liquids.

[1] J. Mannhart and D. Schlom, Science 327, 1607 (2010).
Atomic-scale imaging of complex magnetic orders in quantum materials
Wahl, Prof Peter - gpw2@st-andrews.ac.uk

Many quantum materials exhibit complex magnetic orders, which often are sensitive to external stimuli, such as magnetic field or doping, making them in principle interesting for many technological applications. Characterization of the spatial structure of the magnetic order has mostly been done through Neutron scattering, which however average over a macroscopic sample volume. Spin-polarized scanning tunneling microscope provides real space images of magnetic order at the atomic scale, thereby providing new insights into the spatial structure of the complex magnetic orders. In this project, you will use low temperature scanning tunneling microscopy in a vector magnetic field to characterize the magnetic structure of quantum materials. The studies will aim to establish the surface impact on the magnetic order, knowledge which is critical for technological exploitation and interfacing to other materials, but also to provide a microscopic picture of the magnetic order which will help to identify the dominant contributions to the magnetic interactions in the material. We are in particular interested in metamagnetic phases, where the external magnetic fields can drive phase transitions in the material.

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).
[3] Trainer, et al., Rev. Sci. Instr. 88, 093705 (2017).
Controlling emergent quantum phases through strain-tuning of electronic structure
Hicks , Dr Clifford - cwh10@st-andrews.ac.uk
King, Prof 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.
Dynamical Coulomb blockade in arbitrary environments with backaction
Braunecker, Dr Bernd - bhb@st-andrews.ac.uk

The electron transport through nanostructures is always exposed to the electromagnetic fluctuations of the environment. This is a notable and measurable effect in quantum-coherent conductors, in which the motion of a single electron excites nearby electromagnetic modes which in turn act back on the electrons and cause a nonlinear reduction of the conductance. For weakly transmitting conductors this physics is known as environmental Coulomb blockade and well explained by the “P(E) theory” [1]. But this theory does not extend to highly transmitting conductors in which the transmission time becomes comparable with the environment's reaction time. This regime, the dynamical Coulomb blockade regime, requires to model the environment as a quantum object. For specific conditions important advances have been made over the last few years [2]. But recent experimental work has shown that there is still much unknown in the regime of strong backaction of an arbitrary environment [3]. In this PhD project we will access this physics head-on and derive a modelling of the full counting statistics, which gives access to all current correlators, of a mesoscopic electron system coupled to an arbitrary dynamical quantum enviroment. We will focus on an analytical, non-perturbative many-body modelling of the phenomenon, involving bosonisation similar to [4] and further mappings on scattering type boundary value problems that can be solved with recently developed techniques [5].

[1] G.-L. Ingold and Y. Nazarov, in Single Charge Tunneling ed. by H. Grabert and M. H. Devoret, Ch. 2 (Plenum, 1992).
[2] K. A. Matveev, D. Yue and L. I. Glazman, Phys. Rev. Lett. 71, 3351 (1993); L. W. K. Molenkamp, Flensberg and M. Kemerink, Phys. Rev. Lett. 75, 4282 (1995). Y. V. Nazarov, Phys. Rev. Lett. 82, 1245 (1999); M. Kindermann and Y. V. Nazarov, Phys. Rev. Lett. 91, 136802 (2003); I. Safi and H. Saleur, Phys. Rev. Lett. 93, 126602 (2004); D. S. Golubev, A. V., Galaktionov and A. D. Zaikin, Phys. Rev. B 72, 205417 (2005).
[3] F. D. Parmentier, A. Anthore, S. Jezouin, H. le Sueur, U. Gennser, A. Cavanna, D. Mailly
and F. Pierre, Nat. Phys. 7, 935 (2011).
[4] J.-R. Souquet, I. Safi, and P. Simon, Phys. Rev. B 88, 205419 (2013).
[5] B. A. Muzykantskii and Y. Adamov, Phys. Rev. B 68, 155304 (2003); B. Muzykantskii, N. d'Ambrumenil, and B. Braunecker, Phys. Rev. Lett. 91, 266602 (2003); J. Zhang, Y. Sherkunov, N. d'Ambrumenil, and B. Muzykantskii, Phys. Rev. B 80, 245308 (2009); B. Braunecker, Phys. Rev. B. 73, 075122 (2006).
Electron transport through molecules: A new kind of open quantum system theory (with Dr Erik Gauger, Heriot Watt)
Lovett, Dr Brendon - bwl4@st-andrews.ac.uk

Controlling how electrons flow through molecular structures is key to designing future miniaturised electronic components [1]. Understanding and manipulating such charge transport is a very challenging problem at this nanoscopic scale, especially in the common situation of strong interactions between the charges carriers and the vibrational mode structure of the environment [2]. In this project, you will develop such an understanding using advanced techniques for simulating open quantum systems.

We have recently developed a groundbreaking new theoretical method [3] which relies on a combination of Feynman path integrals and matrix product states, and which opens up the possibility of a multitude of new calculations. The tool that you will develop will be a significant adaptation of this new method, and will describe any quantum problem in which a small system is coupled to both bosonic and fermionic environments.

We hope to reveal new insights into how electron currents in molecules behave, and this will allow us to design new molecular devices that exploit quantum coherence.

[1] S. V. Aradhya and L. Venkataraman, Nat. Nanotechnol. 8 399 (2013).
[2] J. Sowa, J. A. Mol, G. A. D. Briggs, and E. M. Gauger, The Journal of Chemical Physics 149 in press (2018); arXiv:1807.08502
[3] A. Strathearn, P. Kirton, D. Kilda, J. Keeling, and B. W. Lovett. , Nature Communications 9 3322 (2018)
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].
Engineering non-equilibrium material states with cold atoms in optical cavities
Keeling, Dr Jonathan - jmjk@st-andrews.ac.uk

A triumph of 20th century condensed matter physics is the understanding of the phases of matter, arising from interacting many body problems in thermal equilibrium. However, not all matter is in equilibrium, and the understanding of matter out of equilibrium is far less developed. To develop our understanding of this, it is necessary both to develop new theoretical techniques, and to identify clean experimental systems where these approaches can be tested against known problems.

Ultracold atoms have provided an excellent testbed for simulating canonical models in equilibrium, and can be adapted to probe non-equilibrium physics. In particular, ultracold atoms placed in optical cavities can be used to prepare and control non-equilibrium states of matter. Specifically, these experiments involve driving by scattering a pump laser into the optical cavity, leading to cavity mediated interactions between atoms, accompanied with collective dissipation processes. While experiments on atoms single mode cavities have been studied extensively, experiments on multimode cavities are only just beginning. These have the potential to transform the kinds of behaviour one can study.

Our theoretical group collaborates closely with the experimental group of Benjamin Lev (Stanford) who have built a multimode optical cavity[1,2], and are now in the position to use this to explore novel states of matter. Several ideas in this direction have been proposed[3,4,5], including liquid crystaline phases of matter[3], spin glass states [4] and Hopfiled associative memories[5]. However, understanding of the non-equilibrium nature of these phases is yet unclear.

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. We will make use of a variety of analytical and numerical techniques, potentially including matrix product state calculations.



[1] "Tunable-Range, Photon-Mediated Atomic Interactions in Multimode Cavity QED", V. D. Vaidya, Y. Guo, R. M. Kroeze, K. E. Ballantine, A. J. Kollár, J. Keeling, and B. L. Lev, Phys. Rev. X 8 011002 (2018)
[2] "Sinor self-ordering of a quantum gas in a cavity." R. M. Kroeze, Y. Guo, V. D. Vaidya, J. Keeling, B. L. Lev arXiv:1807.04915
[3] "Emergent Crystallinity and Frustration with Bose-Einstein Condensates in Multimode Cavities", S. Gopalakrishnan, B. L. Lev, and P. M. Goldbart, Nat. Phys. 5, 845 (2009).
[4] "Frustration and Glassiness in Spin Models with Cavity-Mediated Interactions." S. Gopalakrishnan, B. L. Lev, and P. M. Goldbart, Phys. Rev. Lett. 107, 277201 (2011).
[5] "Exploring Models of Associative Memory via Cavity Quantum Electrodynamics", S. Gopalakrishnan, B. L. Lev, and P. M. Goldbart, Philos. Mag. 92, 353 (2012).
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)
Fidelity plateaux from correlated noise: beyond the two-state case
Hooley, Dr Chris - cah19@st-andrews.ac.uk

When disorder is studied in the solid state, it is usually considered to be independent of time, and to affect only one parameter of the Hamiltonian (e.g. the on-site energy or the nearest-neighbour hopping amplitude). In the cold-atom context, neither of these assumptions is likely to hold. Disorder will generally be time-dependent, arising for example from the failure of the laser controller to achieve some desired ramp profile. It will also generally appear in a correlated way in multiple parameters of the Hamiltonian.

CM-CDT student Scott Taylor and I have recently shown [1] that this leads to a striking effect, viz. the occurrence of arbitrarily long plateaux in the state-preparation fidelity. However, our work so far has dealt only with the simplest case of a driven two-level system.

The aim of this project is to study the effects of correlated time-dependent disorder in a broader range of Hamiltonians, especially those with a Hilbert space of dimension greater than two. In particular, it aims to connect the abovementioned observation with the phenomenon of many-body localisation [2] and the new phases of matter possible in driven non-equilibrium quantum systems [3].
[1] S.R. Taylor and C.A. Hooley, arXiv:1711.05131 (2017).
[2] R. Nandkishore and D.A. Huse, Annu. Rev. Cond. Matt. Phys. 6, 15 (2015).
[3] F. Harper and R. Roy, Phys. Rev. Lett. 118, 115301 (2017).

Category: Theoretical Hard Condensed Matter
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
High speed spintronics using room-temperature polariton condensates
Ohadi, Dr Hamid - ho35@st-andrews.ac.uk
Samuel, Prof Ifor - idws@st-andrews.ac.uk
Turnbull, Prof Graham - gat@st-andrews.ac.uk

Our aim is to build ultra-highspeed (50 GHz) room-temperature opto-electronic chips based on our recent demonstration of spontaneously magnetised polariton condensates [1,2]. Exciton-polaritons (polaritons) are superpositions of photons in a Fabry-Pérot microcavity and confined excitons in 2-dimensional quantum wells. They are very light (100,000 times lighter than electrons) and very fast (>100 GHz) thanks to their photonic component, but they can also strongly interact with each other due to their excitonic part. Polaritons can form macroscopic quantum states like atomic Bose-Einstein condensates, and using organic materials they can condense at room temperature. In certain conditions, polariton condensates can spontaneously acquire macroscopic spins of up or down. In this project we aim to exploit them to make ultra-highspeed optoelectronic switches and true random number generators on a chip that can be integrated into the next generation of CPUs and telecommunications. You will fabricate electrically contacted organic-based microcavities in close collaboration with Prof. Turnbull and Prof. Samuel’s group, and study the condensation and specifically their spin properties. You are also expected to travel to the sunny island of Crete in Greece for some parts of the fabrication process.

[1] Physical Review X 5, 031002 (2015)
[2] Nature Materials 15, 1074 (2016)

Industry link: Hitachi (http://www.hit.phy.cam.ac.uk/)
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, Prof 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.
Interacting spin lattices of exciton-polariton condensates

One of the most interesting concepts in condensed matter is the so-called “frustration”, where a few spins in the system cannot find an orientation to fully satisfy all the interactions with its neighbouring spins. Frustration is a complex and not well-understood phenomenon with interdisciplinary applications to artificial neural networks as well as material science. The classic example is 3 spins a triangular geometry with antiferromagnetic coupling between the nearest neighbours. We have recently introduced exciton-polariton (polariton) condensates as a new platform to study such spin interactions [1-3]. Polariton condensates are macroscopic quantum states with picosecond dynamics and unique spin properties arising from their nonlinearities. You will experimentally study the spin properties of coupled polariton condensates in 2-dimensional optical lattices in various geometries, specifically the phenomenon of frustration. Your project will also involve a fair amount of programming, and numerical simulations in a collaboration with our theorists.

[1] Physical Review X 5, 031002 (2015)
[2] Physical Review Letters 116, 106403 (2016)
[3] Physical Review Letters 119, 067401 (2017)

Industry link: Hitachi (http://www.hit.phy.cam.ac.uk/)
Interacting spin lattices of exciton-polariton condensates
Ohadi, Dr Hamid - ho35@st-andrews.ac.uk

One of the most interesting concepts in condensed matter is the so-called “frustration”, where a few spins in the system cannot find an orientation to fully satisfy all the interactions with its neighbouring spins. Frustration is a complex and not well-understood phenomenon with interdisciplinary applications to artificial neural networks as well as material science. The classic example is 3 spins a triangular geometry with antiferromagnetic coupling between the nearest neighbours. We have recently introduced exciton-polariton (polariton) condensates as a new platform to study such spin interactions [1-3]. Polariton condensates are macroscopic quantum states with picosecond dynamics and unique spin properties arising from their nonlinearities. You will experimentally study the spin properties of coupled polariton condensates in 2-dimensional optical lattices in various geometries, specifically the phenomenon of frustration. Your project will also involve a fair amount of programming, and numerical simulations in a collaboration with our theorists.

[1] Physical Review X 5, 031002 (2015)
[2] Physical Review Letters 116, 106403 (2016)
[3] Physical Review Letters 119, 067401 (2017)

Industry link: Hitachi (http://www.hit.phy.cam.ac.uk/)
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).


Local control and manipulation of electronic properties of transition metal oxide surfaces
Wahl, Prof 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, at later stages of the project, thin-film samples grown by reactive oxide molecular beam epitaxy will be used.
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.
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)



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)
Path integrals over matrix product states: applications and extensions
Hooley, Dr Chris - cah19@st-andrews.ac.uk

The realisation that the ground states of short-range quantum spin systems can generically be represented by matrix product states is an important recent development in theoretical physics [1]. With the aim of integrating the insights of matrix product states with the powerful tools of quantum field theory, some colleagues and I recently developed a path integral over one-dimensional versions of such states [2].

The aim of this project is threefold: first, to explore the extension of this matrix-product-state path integral to higher-dimensional systems; second, to investigate the nature and physical meaning of instanton processes in such path integrals; and third, to develop further applications of the matrix-product-state path integral to open questions in the physics of frustrated magnetism.

[1] R. Orús, Ann. Phys. 349, 117 (2014).

[2] A.G. Green, C.A. Hooley, J. Keeling, and S.H. Simon, arXiv:1607.01778 (2016).

Category: Theoretical Hard Condensed Matter
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, Prof 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 [4]. 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
[4] Sunko et al., Nature 549 (2017) 492
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]
Shaped pulses for improving the application of electron paramagnetic resonance (EPR) spectroscopy for studying biomolecules
Lovett, Dr Janet - jel20@st-andrews.ac.uk
Smith, Prof Graham - gms@st-andrews.ac.uk

Electron paramagnetic resonance (EPR) spectroscopy is used to investigate the structure of biomolecules such as proteins and nucleic acids (DNA, RNA). It can elucidate the binding site of paramagnetic ions, and can detect dipolar coupling between pairs of paramagnetic centres which relates to the distance between them. The latter method measures nanometre-scale distances using pulsed EPR, and is complementary to other biophysical techniques for measuring structure such as X-ray crystallography, cryo-EM, NMR and FRET.1,2 Recently there has begun a revolution in pulsed EPR with the implementation of arbitrary waveform generators (AWGs) to form shaped pulses.3 This increases the sensitivity, accuracy and scope of the measurements. The spectrometers in St Andrews are about to be upgraded with AWGs. The spectrometers include a Bruker X and high-powered Q-band and the home-built high power W-band spectrometer (HiPER).4,5 The addition of an AWG to HiPER, along with several other scheduled improvements (see recently awarded EPSRC grant EP/R013705/1), will give the world’s most sensitive pulsed EPR spectrometer.

You will test the upgrades to the spectrometers and apply them to solve biological problems.

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 in physics, chemistry, biochemistry, or a related discipline and be motivated to work across the disciplines.

The facilities at St Andrews for EPR, protein preparation and chemistry are outstanding. Informal enquiries are encouraged prior to application and should be made to Dr Janet Lovett (jel20@st-andrews.ac.uk).

1. Jeschke, G., (2012) Annu. Rev. Phys. Chem. 63 419-446.
2. Haugland, M. M, Anderson, E. A., Lovett, J. E., (2016) Electron Paramagnetic Resonance - Volume 25 Editors: Victor Chechik and Damien M. Murphy
3. Spindler, P. E., Glaser, S. J., Skinner, T. E., Prisner, T. F., (2013) Angew Chemie. Int. Ed. 52 3425-3429
4. Cruickshank, P. A. S., Bolton, D. R., Robertson, D. A., Hunter, R. I., Wylde, R. J., Smith, G.M., (2009) Review of Scientific Instruments, 80, 103102
5. 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.
Strong matter-light coupling with novel materials
Keeling, Dr Jonathan - jmjk@st-andrews.ac.uk

Polaritons are quasiparticles resulting from strong coupling between matter and light. Strong coupling occurs for photons confined in a microcavity, so that rather than photon emission being an irreversible loss process, photons that are emitted into the cavity can subsequently coherently excite the material again. This leads to new normal modes, polaritons. [1]

Historically, much of the work on these quasiparticles made use of strong coupling to electronic excitations in inorganic semiconductors, such as GaAs or CdTe. However, recently there has been a lot of interest in polaritons formed from a wide variety of materials, including organic molecules (ranging from small molecules to organic polymer chains), as well as very recent developments for materials such as transition metal dichalcogenides, and hybrid organic-inorganic perovskits. These molecular systems have very strong matter-light coupling, and so the physics can be seen at room temperature. [1,2]

One significant area of research concerns polariton condensation and lasing. Polaritons are bosons, and so Bose-Einstein condensation can be (and has been) seen. Because polaritons are part photon, they have a very low effective mass, leading to a very high transition temperature, indeed with organic materials, this can occur up to room temperature.

Another area of increasing experimental interest is in using strong coupling to change material properties. In the context of organic molecules, this has included the idea of changing chemical reaction rates by strong coupling.

This PhD position will be to explore theoretically models that capture the specific physics of a given material system, and ask how the physics of these materials affects, and is affected by, strong coupling to light. We will look both at the physics of Bose-Condensation, as well as modelling other possible applications of strong matter-light coupling to change material properties. We will make use of a variety of analytical and numerical techniques. For examples of our recent work see Refs. [3-5]

[1] "The new era of polariton condensates." D. W. Snoke and J. Keeling Phys. Today 70 54 (2017)
[2] "The road towards polaritonic devices." D. Sanvitto and S. Kéna-Cohen. Nat. Mater. 15 1061 (2016)
[3] "Organic polariton lasing and the weak- to strong-coupling crossover" A. Strashko, P. Kirton, J. Keeling arXiv:1808.07683
[4] "Orientational alignment in cavity quantum electrodynamics." J. Keeling and P. G. Kirton. Phys. Rev. A 97 053836 (2018)
[5] "Exact States and Spectra of Vibrationally Dressed Polaritons." M. A. Zeb, P. G. Kirton, and J. Keeling. ACS Photonics 5 249 (2018)
Subdiffusive dynamics in the approach to many-body localisation
Hooley, Dr Chris - cah19@st-andrews.ac.uk

The phenomenon of many-body localisation – the failure of ergodicity in certain disordered, interacting many-body quantum systems – has become a major topic of research over the past few years [1]. Recently attention has also become focussed on the approach to this transition from the ergodic side. In particular, it has been shown that spin and energy transport become subdiffusive before the actual many-body-localisation transition is reached [2,3].

Recent work in my research group has concentrated on how universal such subdiffusive phenomena are [4]. In particular, we have begun investigating the connection between the hydrodynamics of the weakly disordered model and the nature of the subdiffusive transport that occurs in the approach to full localisation. The aim of this project is twofold: first, to extend those numerical studies to a larger class of one-dimensional models, and second, to draw on existing literature on the nonlinear Schrödinger equation [5] to explore the development of an analytical theory of this subdiffusive regime.

[1] R. Nandkishore and D.A. Huse, Annu. Rev. Cond. Matt. Phys. 6, 15 (2015).

[2] M. Žnidaric, A. Scardicchio, and V.K. Varma, Phys. Rev. Lett. 117, 040601 (2016).

3] V.K. Varma, A. Lerose, F. Pietracaprina, J. Goold, and A. Scardicchio, J. Stat. Mech. (2017) 053101.

[4] M. Schulz, S.R. Taylor, A. Scardicchio, and C.A. Hooley, in preparation.

[5] A. Iomin, Phys. Rev. E 81, 017601 (2010).

Category: Theoretical Hard Condensed Matter
Theory of Quantum Light Sources: how can we make coherent single photons in solid state systems?
Lovett, Dr Brendon - bwl4@st-andrews.ac.uk

The generation of indistinguishable single photons on demand is a key requirement for many kinds of future quantum technologies, such as secure communication and optical quantum computing [1]. Being able to make coherent quantum light sources in solid state systems would enable us to create on-chip photonic circuits that would enable this technology. It is therefore of the utmost importance to understand what effect a solid state environment has on the fidelity of emitted photons.

In this project, you will exploit and developing a groundbreaking new technique our group has created for simulating open quantum systems [2]. Based on a combination of Feynman's path integrals [3,4] and matrix product states [5], it has already enabled calculations impossible by more traditional means. You will study how the technique might be used to calculate the photon correlation functions that characterise a single photon source, in the presence of a strongly-coupled environment of vibrational modes of the crystal. You will go on to study how a photonic cavity might be used to improve the performance of such a device.
Topological physics beneath magnetic structures and interfaces on superconductors
Braunecker, Dr Bernd - bhb@st-andrews.ac.uk

It has been known for a long time that magnetic impurities induce bound states in superconductors [1] but only in recent years it was realised that lining up such states [2] can lead to a twist in the resulting wave function that is known as a changed topological index. The study of such topological states has by now become a highly active field of research. A strong promotor is the rather recent insight that any quantum technology will have to rely on some form of topological states. In this PhD project we will investigate how topological properties appear at interfaces or magnetic structures embedded on superconductors, in a set-up where a strict dimensional decoupling as considered by most approaches is not possible. This will build on our recent work [3]. A particular emphasis will be given to interactions between the states generated by the interaction between the magnetic scatterers and the superconductor, and to particular instabilities that can lead to novel quantum phases.

[1] L. Yu, Acta Phys. Sin. 21, 75 (1965); H. Shiba, Prog. Theor. Phys. 40, 435 (1968); A. I. Rusinov, JETP Lett. 9, 85 (1969).
[2] F. Pientka, L. I. Glazman, and F. von Oppen, Phys. Rev. B 88, 155420 (2013); S. Nadj-Perge, I. K. Drozdov, J. Li, H. Chen, S. Jeon, J. Seo, A. H. MacDonald, B. A. Bernevig, and A. Yazdani.
Science 346, 6209 (2014).
[3] C. J. F. Carroll and B. Braunecker, arXiv:1709.06093.
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.
Unveiling the structure of long RNAs using EPR Spectroscopy
Lovett, Dr Janet - jel20@st-andrews.ac.uk

**This project is fully funded and must start on, or before, 27th September 2018 - applications are welcome immediately.**

Electron paramagnetic resonance (EPR) spectroscopy can measure nanometre distances with Angstrom precision. Applying this to the structural-elucidation of RNA has great potential for the progression of our understanding of fundamental processes and for the future of targeted drug discovery. However, in order to apply EPR, the RNA must have a paramagnetic probe – a spin label – attached. While this can be achieved with solid-phase synthesis methods this restricts the RNA length to less than c.a. 50 nucleotides.

This project will explore a bioconjugation method to enable the labelling of long RNAs. You will prepare known and novel nucleotides and spin labels and then test these both in solid-phase synthesis and for their suitability in bioconjugation. The synthetic chemistry will be learned in the groups of collaborators Professors Edward Anderson and Tom Brown in Oxford, UK during a series of visits. These methods will be employed in St Andrews in the excellent labs of Professor David O’Hagan for further preparations. The long RNA synthesis will be in collaboration with Dr Carlos Penedo in St Andrews. St Andrews has excellent EPR facilities for the measurements.

You must have a good scientific degree and be competent in organic synthesis methods. The PhD will enable you to gain more organic synthesis skills as well as broaden your skill set to biosynthesis and applications of EPR spectroscopy. The work carried out here will enable cutting-edge EPR methods to be applied to the study of long RNAs which will have impact for both the fundamental research into their structure and function relations and also for drug discovery and nanotechnology.

St Andrews University is situated in the beautiful and bustling seaside town of St Andrews with stunning beaches, a great history and tradition and close to Edinburgh, Dundee and the wider attractions of Scotland. The School of Physics and Astronomy at St Andrews (joint with Edinburgh) was ranked 3rd in the UK in the latest Research Excellence Framework (REF) exercise.

Funding Notes
The PhD studentship is open to candidates from the UK and wider EU with fees and stipend fully covered for four years. The project is funded by The Royal Society of London. The start date must be on, or before, 27th September 2018 - applications are welcome immediately.
References
Haugland et al, Journal of the American Chemical Society (JACS), 2016, 138, pages 9069-9072 (DOI: 10.1021/jacs.6b05421)


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.
Advanced microscopy of nanolaser particles
Schubert, Dr Marcel - ms293@st-andrews.ac.uk

*Opportunity for UK, EU and international students*

**This project must commence before 28th February 2019 - applications are welcome immediately**

Nano- and microlasers have recently gained attention as novel light sources for biomedical applications, including single cell barcoding, refractive index sensing and tissue-integrated pressure sensors [1-3]. Their unique properties renders these devices ideally suited for experiments inside living specimens where many physical process related to development and disease are poorly understood.

Over the past decade, light sheet microscopy has revolutionized our understanding of the development of complex biological organisms [4]. While representing one of the most powerful and innovative microscopy techniques, light sheet microscopes are also typically build from scratch which allows to integrate a vast range of imaging modalities.

In this project, advanced 3D imaging will be combined with the broad capabilities of bio-integrated nanolaser. The goal is to correlate the spectroscopic information of the nanolasers with structural properties of the biological sample, by building a custom-made light sheet microscope. The new instrument will be used to investigate important biological processes like e.g. single cell tracking of invasive circulating tumour cells, cardiac regeneration or pressure sensing during gastrulation. Other aspects of the project are related to applying techniques to reduce effects of scattering by using advanced beam shaping techniques. Good knowledge of optics and microscopy, as well as basic programming skills are preferred but the student will be given the opportunity to learn relevant techniques during the project.

For further information please contact Marcel Schubert [ms293@st-andrews.ac.uk] prior to application.

[1] M. Schubert, A. Steude, P. Liehm, N. M. Kronenberg, M. Karl, E. C. Campbell, S. J. Powis, M. C. Gather, Lasing within Live Cells Containing Intracellular Optical Microresonators for Barcode-Type Cell Tagging and Tracking, Nano Lett. 2015, 15, 5647.

[2] M. Schubert, K. Volckaert, M. Karl, A. Morton, P. Liehm, G. B. Miles, S. J. Powis, M. C. Gather, Lasing in Live Mitotic and Non-Phagocytic Cells by Efficient Delivery of Microresonators, Sci. Rep. 2017, 7, 40877.

[3] A. H. Fikouras, M. Schubert, M. Karl, J. D. Kumar, S. J. Powis, A. di Falco, M. C. Gather, Non-obstructive intracellular nanolasers, arXiv:1806.03366, 2018.

[4] T.-L. Liu et al., Observing the cell in its native state: Imaging subcellular dynamics in multicellular organisms, Science 2018, 360, eaaq1392.
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, Prof 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.

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 further quantum field theory effects in curved spacetime.
High resolution coherent imaging with sub-millimetre wave radar
Robertson, Dr Duncan - dar@st-andrews.ac.uk

This PhD is funded as an EPSRC CASE studentship in conjunction with QinetiQ Ltd.

**If you are interested in this PhD please contact Dr Robertson.**


Background
Until recently the use of the region of the RF spectrum termed ‘sub-millimetre wave’ (300 to 1000GHz) has received little attention. It sits between the millimetre wave (30 to 300GHz) and Terahertz (>1000GHz) bands where radar and spectroscopy techniques are well-established. QinetiQ is recognised as a World leader in radar techniques applied to predominantly military and security applications at frequencies up to 94GHz. An internally funded QinetiQ study into low Terahertz applications has identified the region between 100 and 400GHz as suitable for extending QinetiQ’s radar capabilities and opens up new opportunities not feasible at lower frequencies. Currently, QinetiQ has no RF capability above 100GHz, in particular, component technology and facilities to carry out work at these frequencies. QinetiQ has strong capability in signal processing techniques and providing innovative, bespoke radar solutions for challenging radar requirements.

The University of St Andrews is one of 2 universities in the UK with strong radar capabilities at sub-millimetre wave frequencies and has demonstrated radars at 220GHz and 340GHz. The PhD is designed to build on the University’s practical capabilities and experience at frequencies up to 400GHz and on QinetiQ’s knowledge of the military and security domains and experience of synthetic aperture radar (SAR).

Scope of the PhD
Radar at sub-millimetre wave frequencies offers new opportunities by exploiting the high angular and range resolutions to provide detailed coherent imaging in a compact physical envelope. Until recently devices for power generation, receiver elements and antennas have been either experimental or prohibitively expensive and achievable radar performance has been limited by noise figure, power generation, propagation characteristics and manufacturability. Currently the main applications are for short range automotive radar and for concealed weapon and IED detection. QinetiQ has an interest in military and security applications especially for imaging difficult targets.

The PhD is intended to investigate novel techniques to use sub-millimetre wave radar to provide very high resolution, coherent imaging against ‘difficult’ targets. ‘Difficult’ includes targets with low radar cross section, fluctuating targets and targets that are difficult to discriminate against other targets. Specifically, this is likely to include change detection techniques, motion compensation, complex SAR imaging and auto-focusing. The scope is focused on SAR but could include real-beam imaging.

It is envisaged, budget permitting, that a linear, rail-mounted sub-millimetre wave radar system will be constructed to record measurements and to evaluate algorithms developed during the PhD. The PhD shall also explore the limits of range resolution, with bandwidths >10GHz, and how this relates to the capability to discriminate and characterise targets. If necessary for a particular application, polarisation and propagation effects shall be considered.

QinetiQ hopes to increase its understanding of the capabilities of sub-millimetre wave radar and, subject to IP considerations, develop the ideas generated into military and security applications. Here are some examples of the types of application that QinetiQ would be interested in;
• Characterisation of surface texture and features, for example, detecting wear and tear on road and airport runway surfaces
• Detection of targets in a high clutter environment, perhaps through gaps or transparent materials
• Geolocation using SAR and/or multiple sensors
• Imaging to detect variations in surfaces, moisture content, cracks in buildings, vegetation, man-made vs natural features, wave profiling
• Vibrometry for engine vibration, fault detection
• Detecting very slight movements of objects exploiting Doppler
• Mounting a sub-millimetre wave radar on an unmanned air vehicle (UAV)

The majority of the PhD work shall be carried out at The School of Physics and Astronomy at St Andrew’s but a minimum of 3 months in total shall be carried out working with the SAR group at Malvern. Working at Malvern will require security clearance although no information disclosed under the PhD will be classified. The requirement for security clearance means that UK nationality is preferred.

Integrated Magnetic Resonance Doctoral Training Centre
Smith, Prof 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.

Integrating nanolasers into 3D cardiac cultures
Schubert, Dr Marcel - ms293@st-andrews.ac.uk

Growth of functional cardiac tissue and stem cell therapies hold great promise to overcome the limited ability of the human heart to repair itself. However, current progress is strongly limited by the ability to investigate mechanical coupling between transplanted cells and the host environment.

We have recently developed a new method to detect contractions of single heart cells. By integrating micro- or nanoscopic lasers into individual cells the contractile properties of heart cells can be recorded optically [1-3]. The aim of this project is to develop a tissue integrated platform to detect contraction profiles of individual cells in natural and artificial heart muscles. To reach this goal, new microscopic lasers will be developed with optimized spectral and mechanical properties to facilitate long-term integration up to the point where these devices can be applied in-vivo. A passion for optics and biology are recommended to drive this exciting and truly multi-disciplinary project which is most suitable for graduates with a background in physical science, material science or bioengineering.

For further information please contact Marcel Schubert [ms293@st-andrews.ac.uk] prior to application.

[1] M. Schubert, A. Steude, P. Liehm, N. M. Kronenberg, M. Karl, E. C. Campbell, S. J. Powis, M. C. Gather, Lasing within Live Cells Containing Intracellular Optical Microresonators for Barcode-Type Cell Tagging and Tracking, Nano Lett. 2015, 15, 5647.

[2] A. H. Fikouras, M. Schubert, M. Karl, J. D. Kumar, S. J. Powis, A. di Falco, M. C. Gather, Non-obstructive intracellular nanolasers, arXiv:1806.03366, 2018.

[3] M. Karl, J. M. E. Glackin, M. Schubert, N. M. Kronenberg, G. A. Turnbull, I. D. W. Samuel, M. C. Gather, Flexible and ultra-lightweight polymer membrane lasers, Nat. Commun. 2018, 9, 1525.
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
MM-wave Radar, Components and Techniques
Smith, Prof 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.

 
Non-reciprocal optics
Schulz, Dr Sebastian - sas35@st-andrews.ac.uk

In contrast to traditional, reciprocal optical systems, non-reciprocal systems allow the realization of interesting physical effects, for example optical isolation or the breaking of seemingly fundamental physical limits, such as the link between a system’s delay and its bandwidth [1]. Typically, non-reciprocal optical elements are realized using magneto-optic materials, for example in a Faraday Rotator. However, these materials are not suitable for integration in nanophotonic devices and thus new methods of achieving non-reciprocity need to be explored, for example nonlinear optical effects or time-variant modulations [2-4].

This project addresses the realization of on-chip non-reciprocal optical elements, new applications enabled by these elements and the exciting new physics achieved by combining non-reciprocal elements with components such as absorbers, emitters or resonators [1].

You are expected to have an interest in studying fundamental concepts in physics as well as mastering hands on nanofabrication and laboratory techniques. The project includes collaborations with groups across Europe and North America, offering you opportunities to visit the laboratories of collaborators and to build your own professional network.

The project will be supervised by Dr. Sebastian Schulz, who will join the department in March 2018. For more details on this topic and for any question regarding the project, please contact Dr. Sebastian Schulz (Sebastian.Schulz@cit.ie).

[1] H. Tsakmakidis, L. Shen, S. A. Schulz, X. Zheng, J. Upham, X. Deng, H. Altug, A. F. Vakakis and R. W. Boyd “Breaking Lorentz reciprocity to overcome the time-bandwidth limit in physics and engineering” Science 356, pp1260-1264 (2017). http://science.sciencemag.org/content/356/6344/1260

[2] E. A. Kittlaus, N. T. Otterstrom and P. Rakich “On-chip inter-modal Brillouin Scattering” Nature Communications 8, p.15819 (2017). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5504300/

[3] L. Feng, M. Ayache, J. Huang, Y.-L. Xu, M.-H. Lu, Y.-F. Chen, Y. Fainman and A. Scherer “Nonreciprocal Light Propagation in Silicon Photonic Circuit” Science 333, p. 729 (2011). http://science.sciencemag.org/content/333/6043/729

[4] D. L. Sounas and A. Alu “Non-reciprocal photonics based on time modulation” Nature Photonics 11, p 774 (2017). https://www.nature.com/articles/s41566-017-0051-x
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.
Nonlinear optics using Epsilon-near-zero materials
Schulz, Dr Sebastian - sas35@st-andrews.ac.uk

In Epsilon-near-zero (ENZ) [1] materials, for a certain spectral region, the electric permittivity, epsilon, is below 1, i.e. smaller than that of free space/air. The small epsilon results in strange optical properties and offers great potential for linear and non-linear optical applications. For example, the low values of epsilon imply that there is no (or little) phase advancement within the material and therefore the requirement for phase matching of non-linear optical processes is removed.

This project will address the use of transition metal oxides, such as Indium Tin Oxide as ENZ materials [2]. In these materials, the ENZ spectral region can be controlled by the growth conditions and deposited films can be combined with optical elements to form tailor made metamaterials and devices [3,4] with tailored optical properties.

You will be expected to deposit and characterise ENZ material films, design composite optical elements consisting of ENZ films coupled to nanophotonic devices, for example antenna arrays or individual resonators, to create tailored optical responses. You will gain a deep understanding of one of the most exciting new fields in optics, gain expertise in optical simulation, nanofabrication and characterisation techniques and work in an international collaboration, allowing you to build your own professional network.

The project will be supervised by Dr. Sebastian Schulz, who will join the department in March 2018. For more details on this topic and for any question regarding the project, please contact Dr. Sebastian Schulz (Sebastian.Schulz@cit.ie).

[1] N. Engheta “Pursuing Near-Zero Response” Science 340, pp 286-287 (2013). http://science.sciencemag.org/content/340/6130/286

[2] M. Z. Alam, I. De Leon and R. W. Boyd “Large optical nonlinearity of indium tin oxide in its epsilon-near-zero region” Science 352, p 795 (2016). http://science.sciencemag.org/content/352/6287/795

[3] S. A. Schulz, A. A. Tahir, M. Z. Alam, J. Upham, I. De Leon and R. W. Boyd “Optical response of dipole antennas on an epsilon-near-zero substrate” Physical Review A 93, 063846 (2016). https://journals.aps.org/pra/abstract/10.1103/PhysRevA.93.063846

[4] M. Z. Alam, S. A. Schulz, J. Upham, I De Leon and R. W. Boyd manuscript accepted for publication.
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 Imaging of Biological Specimens
Brown, Prof Tom - ctab@st-andrews.ac.uk

ptical imaging can provide detailed information about a range of biological specimens from whole animals to small tissue samples. A drawback however is that such imaging often only provides data from structures at or near the surface. By contrast Optical Coherence Tomography (OCT), a low coherence interference imaging technique, can provide detailed information on tissue structure at depths of a few mm with resolution of around 10 um in living animals.

In this project we will apply OCT to a range of biological specimens to provide information which has proved to be unobtainable using other techniques. In particular the project will use OCT to provide information on tissue regeneration in amphioxus (fish-like marine chordates with close affinity to vertebrates) which are used as a model for testing concepts in nerve cord growth and repair. We will also apply OCT to Antarctic Krill (Euphasia superba), perhaps the key species in the Antarctic food web. The information these studies provide will be used to develop advanced models for acoustic imaging Krill and may also support studies on the effects of global climate change on this key species. We may also apply the system to recently launched studies of surface vasculature in Southern Elephant Seals to support ongoing studies into the diving physiology of this species.

The projects described are interdisciplinary and will require an open mind and a willingness to work with partners within Biology and Marine Science in the UK and at the Australian Antarctic Division. Australia. In order to fully develop our systems and to enable in vivo testing some travel and extended stays may be required to partner institutions.

The main supervisor for the project will be Professor Tom Brown in the School of Physics, with co-supervision by Dr Ildiko Somorjai within the School of Biology.

Prospective students should have a good background in Physics with an interest in applying their work in other fields. We are also interested in applications from students in Biology who have a strong background in imaging techniques.

Examples of the application of OCT to Krill can be found at:

M.J. Cox, S. Kawaguchi, R. King, K.Dholakia and C.T.A. Brown, “Internal physiology of live krill revealed using new aquaria techniques and mixed optical microscopy and optical coherence tomography (OCT) imaging techniques”, Marine and Freshwater Behaviour and Physiology, 48, p. 455 (2015)

N. Bellini, M.J. Cox, D.J. Harper, S.R. Stott, P.C. Ashok, K. Dholakia, S. Kawaguchi, R. King, T. Horton and C.T.A. Brown, “The Application of Optical Coherence Tomography to Image Subsurface Tissue Structure of Antarctic Krill Euphausia superba”, PLOS ONE, 9, Art. No. e110367 (2014
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.
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 redefining the 140 years old optical resolution limit theorem to include recent new developments such as those based on non-linearity, structured illumination, propagation of the optical degrees of freedom and compressive sensing. The project is theoretical in nature where the beams are numerically modelled to determining their resolving powers in the different configurations. The project can also have an experimental component where the novel theoretical understanding is checked in the lab. 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? How can compressive sensing be used to overcome this limit?
SAGES: The application of millimetre wave radar to the study of volcano-glacier interactions and ice-ocean interactions in conditions of reduced visibility
Robertson, Dr Duncan - dar@st-andrews.ac.uk

This PhD will be part funded by SAGES, the Scottish Alliance for Geoscience, Environment and Society (http://www.sages.ac.uk/), in a competitive process. ** The closing date for applications is January 26th 2018.** Interviews are schedule for 19-21 February 2018 and will take place in Edinburgh.

The remaining funding will be provided by an EPSRC Doctoral Training Partnership studentship.

**If you are interested in this PhD please contact Dr Robertson well before the closing date.**


The overall aim of this PhD is to develop the use of millimetre wave radar for applications in geosciences, focusing on volcano-glacier and ice-ocean interactions.

Millimetre wave radar offers a key advantage over conventional optical survey methods in its ability to map terrain with high resolution whilst operating in conditions of reduced visibility. The AVTIS radars developed at UStA by Macfarlane & Robertson for volcano imaging [1] have demonstrated the potential for such instruments to map topographic change on volcanoes through complete obscuration (e.g. ash, clouds). In addition to topography, the millimetre wave radar can measure reflectivity and the velocity of moving targets, including high spatio-temporal resolution mapping of rainfall.

DEM extraction and the discrimination between terrain types based on reflectivity, or normalised radar cross section (NRCS), will be developed and refined for improved classification of different terrain surface types. These are central to the study of volcano-glacier interactions and related hazards, which are still poorly understood (e.g. the 2010 Eyjafjallajökull eruption) as critical periods of activity during eruptions are often obscured. The AVTIS radar will elucidate changes in the volcano and glacier geometries, impacting eruption timing, magnitude or meltwater-induced mass movements e.g. lahars. The first case study will thus target ice-capped volcanoes (e.g. Iceland).

The calving of icebergs at the margins of glaciers and ice sheets is critical to our understanding of the near future contribution of the Greenland Ice Sheet to sea level rise. Continuous monitoring of grounded ice margins under conditions of heavy cloud cover and precipitation is thus needed, where conventional techniques (LIDAR and time lapse photography) are rendered useless. The ability of the millimetre wave radar to generate DEMs under these conditions will be invaluable. The second stage of the project will thus be glacier mapping with the AVTIS-2 radar, which has never previously been reported in the literature.

The project will follow broadly this structure:

* Develop improved DEM extraction methodology using existing AVTIS data. Initially using LIDAR data from a coincident survey of a local quarry as ground truth, methods for DEM surface extraction from the AVTIS radar data sensing volume will be investigated and refined. These new methods will be evaluated against existing AVTIS datasets (mainly data from the Soufriere Hills Volcano, Montserrat). Additional data for algorithm development can also be acquired locally.

* Develop terrain classification algorithms based on analysis of existing AVTIS data and rough surface scattering models, tested on the extensive AVTIS data set, which already includes volcanic terrain and locally acquired data e.g. Rest and Be Thankful, Argyll; Lomond Hills Fife; Old Man of Storr, Skye.

* Gather millimetre wave NRCS data of glacier ice as function of incidence angle using the AVTIS-2 radar on field campaign to e.g. Iceland and develop an empirical model suitable for radar performance prediction.

* Collect the first mm-wave radar DEMs of glaciers using AVTIS-2 and quantitatively compare with contemporaneously acquired lidar (terrestrial laser scanned) DEMs.

* Explore the new interpretational potential of the instrument in terms of volcano-ice and ice-ocean interactions

[1] Macfarlane, D.G., Odbert, H.M., Robertson, D.A., James, M.R., Pinkerton, H. & Wadge, G., “Topographic and thermal mapping of volcanic terrain using the AVTIS ground based 94GHz dual-mode radar/radiometric imager”, IEEE Trans. Geosci. Rem. Sens., 51, (1), 2013, pp. 455 - 472.


The supervisory team for this PhD will consist of:-
Dr Duncan A. Robertson [Director of Studies], Dr David G. Macfarlane: School of Physics & Astronomy, University of St Andrews (physics / mm-wave radar)
Dr Brice Rea, Dr Matteo Spagnolo: School of Geoscience, University of Aberdeen (glaciology/spatial analysis)
Dr Luca De Siena: School of Geoscience, University of Aberdeen (volcanology)
Prof. Doug Benn: School of Geography & Sustainable Development, University of St Andrews (glaciology)

The successful candidate should be highly numerate and have, or expect to have, a UK Honours Degree at 2.1 or above, or equivalent, in a relevant subject area (e.g. geophysics, physical geography, environmental science, geology, electronic engineering, physics).

Single-molecule spectroscopy of organic semiconducting polymers
Penedo-Esteiro, Dr Carlos - jcp10@st-andrews.ac.uk
Samuel, Prof Ifor - idws@st-andrews.ac.uk

Organic semiconductors based on light-emitting conjugated polymers are attracting considerable interest in semiconductor physics and are emerging as exceptional ‘plastic-like’ materials for optoelectronic applications including displays, lasers and solar cells. We have recently reported the first single-molecule studies regarding the conformation of individual polymer chains in organic solvents commonly used for device fabrication [1 ,2]. Now, in this project, we aim to combine this observation method based on single molecule fluorescence spectroscopy with magnetic tweezers to apply force to the polymer chain. By merging both techniques we will be able to stretch the polymer chain at will and understand in more detail how the conformation of the polymer chain impacts its light-emission properties. The results will help to develop new solution-processing methods that improve device performance. The project is a collaboration between the groups of Prof Ifor Samuel and Dr Carlos Penedo

[1] Dalgarno, Paul A., Christopher A. Traina, J. Carlos Penedo, Guillermo C. Bazan, and Ifor D. W. Samuel. 2013. “Solution-Based Single Molecule Imaging of Surface-Immobilized Conjugated Polymers.” Journal of the American Chemical Society 135 (19): 7187–93.
[2] Tenopala-Carmona, F., S. Fronk, Gui Bazan, Ifor DW Samuel, J. Carlos Penedo. (2018) Real-time observation of conformational switching in single conjugated polymer chains. Sci. Adv. In press

Slow and structured light in nanophotonics
Schulz, Dr Sebastian - sas35@st-andrews.ac.uk

Slow light waveguides have the potential to strongly enhance light matter interactions, leading to efficient non-linear optical processes, optical switches and optical modulators amongst other applications [1]. On a photonic chip slow light is typically realized through Photonic Crystal waveguides or coupled optical resonator waveguides [2], with the speed of light typically between 1/ 10 and 1/100 of the free space value. However, all these realizations suffer from optical scattering from fabrication defects [2-4], leading to optical losses and light localization, limiting the current device performance and rendering physical concepts such as the group velocity meaningless. Yet at the same time optical information can travel through completely opaque materials, implying that the current limit – not using photonic devices in the strong scattering regime - is self-imposed.

In this project you will investigate new slow light waveguide designs, leading to further reductions in the group velocity, while simultaneously reducing the optical losses and scattering. You will address fundamental questions about the behaviour of light and information in scattering media, for example: “At what velocity does information travel through a disordered system and how is this dependent on the disorder level in the system?”. You will investigate the effect of slow light on topics at the forefront of integrated photonics research, for example the use of complex polarization states in integrated optics and how this is affected by the disorder present in real world systems.

You will learn nanofabrication, optical simulation and characterisation techniques and gain a deep understanding of complex physical systems. You will interact with collaborators both in the UK and abroad, giving you the opportunity to visit their laboratories and build your own professional network.

The project will be supervised by Dr. Sebastian Schulz, who will join the department in March 2018. For more details on this topic and for any question regarding the project, please contact Dr. Sebastian Schulz (Sebastian.Schulz@cit.ie).

[1] T. F. Krauss “Why do we need slow light” Nature Photonics 2, p 448-450 (2008). https://www.nature.com/articles/nphoton.2008.139
[2] S. A. Schulz, L. O’Faolain, D. M. Beggs, T. P. White, A. Melloni and T. F. Krauss “Dispersion engineered slow light in photonic crystals: a comparison” Journal of Optics 12, 104004 (2010). http://iopscience.iop.org/article/10.1088/2040-8978/12/10/104004/meta
[3] S. Mazoyer, J. P. Hugonin and P. Lalanne “Disorder-induced Multiple scattering in Photonic-Crystal Waveguides” Physical Review Letters 103, 063903 (2009). https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.103.063903
[4] L. O’Faolain, S. A. Schulz, D. M. Beggs, T. P. White, M. Spasenovic, L. Kuipers, F. Morichetti, A. Melloni, S. Mazoyer, J. P. Hugonin, P. Lalanne and T. F. Krauss “Loss engineered slow light waveguides” Optics Express 18, pp.27627-27638 (2010). https://doi.org/10.1364/OE.18.027627
The Development of Ultrafast Laser Systems
Brown, Prof Tom - ctab@st-andrews.ac.uk

Ultrafast laser systems generate short pulses of light which may last on a few femtoseconds (fs.) These lasers are used in a wide range of applications from highly sensitive metrology to the 3D imaging of biological specimens.

In this project, we will continue our develops of ultrafast laser systems based on novel-glass gain media supplied by our partners within the UK. The student will be responsible for the design and operation of new laser systems. We will also use these systems to test advanced new components including saturable absorbers based on e.g. graphene and MoS2 and testing new approaches for dispersion compensation. As the project progresses we will also investigate the development of integrated ultrafast sources combining with other staff in the School of Physics and Astronomy and further afield. The lasers developed will be used in a range of new applications including the development of new techniques in dentistry where we will replace worn out enamel using laser sintered materials.

Students undertaking this project should have an interest in lasers and photonics systems. Experience of work within an advanced photonics laboratory would be advantageous (though not necessary) and students should be prepared to work closely with collaborators around the work to develop the laser systems.

Examples of previous work within the group can be seen at:

A. Choudhary, A.A. Lagatsky, Z.Y. Yang, K.J. Zhou, Q. Wang, R.A. Hogg, K. Pradeesh, E.U. Rafailov, W. Sibbett and C.T.A. Brown, “A diode-pumped 1.5 mu m waveguide laser mode-locked at 6.8 GHz by a quantum dot SESAM”, Laser Physics Letters, 10, Art. No. 105803 (2013)

N.K. Metzger, C.R. Su, T.J. Edwards and C.T.A. Brown, “Algorithm based comparison between the integral method and harmonic analysis of the timing jitter of diode-based and solid-state pulsed laser sources”, Optics Communications, 341, p.7 (2015)

A.D. Anastasiou, S. Strafford, O. Posada-Estefan, C.L. Thomson, S.A. Hussain, T.J. Edwards, M. Malinowski, N. Hondow, N.K. Metzger, C.T.A. Brown, M.N. Routledge, A.P. Brown, M.S. Duggal and A. Jha, “β-pyrophosphate; a potential biomaterial for dental applications”, In Press, Materials Science & Engineering C (2017)


A.A. Lagatsky, Z. Sun, T.S. Kulmala, R.S. Sundaram, S. Milana, F. Torrisi, O.L. Antipov, Y. Lee, J.H. Ahn, C.T.A. Brown, W. Sibbett and A.C. Ferrari, “2 µm solid-state laser mode-locked by single-layer graphene”, Applied Physics Letters, 102, Art. No. 013113 (2013)
Ultrafast spectroscopy of Whispering Gallery Mode Nanolasers
Gather, Prof Malte - mcg6@st-andrews.ac.uk
Schubert, Dr Marcel - ms293@st-andrews.ac.uk

Laser miniaturization has advanced to the point where lasers can be integrated into individual biological cells [1,2]. Enclosed by the cells, these lasers have been proposed as multifunctional light sources that allow to identify and track single cells or to optically sense physiological changes. However, future applications of intracellular lasers in large biological systems require data acquisition and throughput orders of magnitudes above state of the art methods.

To overcome the current limitations in detecting lasing spectra with high temporal and spectral resolution, a novel approach will be developed, tested and implemented into a confocal microscope. The newly designed instrument will then be used to acquire 3D maps of tissue-integrated nanolasers alongside with high resolution microscopy images.
The project offers a unique opportunity to gain knowledge of advanced photonic techniques as well as working with biological model systems. Good knowledge of optics and basic experience with software programming are recommended to drive this project.

For further information please contact Marcel Schubert [ms293@st-andrews.ac.uk] or Malte Gather [mcg6@st-andrews.ac.uk] prior to application.

[1] M. Schubert, A. Steude, P. Liehm, N. M. Kronenberg, M. Karl, E. C. Campbell, S. J. Powis, M. C. Gather, Lasing within Live Cells Containing Intracellular Optical Microresonators for Barcode-Type Cell Tagging and Tracking, Nano Lett. 2015, 15, 5647.

[2] A. H. Fikouras, M. Schubert, M. Karl, J. D. Kumar, S. J. Powis, A. di Falco, M. C. Gather, Non-obstructive intracellular nanolasers, arXiv:1806.03366, 2018.