We are always looking for excellent and highly motivated PhD students
and postdocs. If you are interested the best is to make a first informal
contact with Bernd Braunecker.
After some exchange or a discussion it is usually clear how to proceed.
The only criterium we use to select candidates is excellence, and it
does not matter for us who you are and from where you come. If you are
good and enthusiastic, if we have the capacity and if we can secure funding
then you are welcome. Condensed matter physics has still a large deficit of
women though, and we wish to encourage you specifically to apply.
Please feel free to get in touch with Bernd Braunecker
at any time, even if you are undecided
about whether it would be the good place or a good idea to do a PhD.
If you wish to proceed with an official application you can use the
official application site of the School of Physics and Astronomy.
Your first approach should be to not worry about funding and just contact us or apply.
Listed below are, however, some scholarships that may be of interest if you come from one
of these countries.
For students from the mainland China a number of PhD fellowships is available through the
China Scholarship Council, and details can be found on the dedicated website on the
CSC programme
of the university. Check out the closing dates carefully (as they tend to change
considerably). Notice that an offer from St Andrews must be made before the CSC
makes its selection. This means you should contact us well in advance to the deadline.
Notice also that a proof of fluency in English is required already at the stage of application.
Additional scholarships for applicants for Commonwealth countries may be available through the
international
Commonwealth Scholarship and Fellowship Plan.
There are various programmes depending on the country of origin. Deadlines are usually
once per year but the closing date is different for each programme, and the availability of
a specific programme is also a fluctuating factor unfortunately.
The university has a page on
postgraduate funding that has a considerable list of funding opportunities.
Whenever there is an opening sponsored through us it will be announced
here.
Potential PhD projects
The descriptions below contain some potential PhD projects.
Notice that these projects are mainly indicative. The fields of research are evolving
rapidly and new interesting topics are coming up quickly. Adjustments following your interests
are also always possible.
We are in addition very open to discuss other projects if they are promising for everyone involved.
Decoherence, the enemy of any quantum processing, is the uncontrolled decay of a well defined quantum superposition.
It occurs because any quantum system is always embedded in a wider environment with a macroscopic number of degrees
of freedom. The interaction with these degrees of freedom causes a destructive interference and a nicely prepared
quantum superposition dissipates somewhere in the environment. Large efforts are thus made throughout the world to
isolate the system from its environment, to use special driving protocols that reverse some of the destructive
interference, etc.
However, the concept of "bad" can also be reversed into something "good". It is indeed interesting to ask how exactly
decoherence builds up, if we can use this to learn something about the system and the environment, and even if there
is a way to use this knowledge for quantum information processing. Indeed the quantum fluctuations that eventually turn
into decoherence initially build up an entanglement with the environment. The main questions underlying this PhD project
are how this happens, how it can be followed in time, and if we can use it in a controlled way.
As a first example we have worked out in detail how a spin decays in a metal [1]. The stationary properties of such a
system are known since very long and the analysis of the thermal decay is on the basis of magnetic resonance techniques
such as NMR or MRI. However, mostly left aside was the regime of very short time scales in which the spin and a part of
the metallic environment have a joint coherent evolution, and in which coherent excitations in the metal act back on the
spin dynamics. The coherent many-body effect of a local excitation, such as from a spin flip, on the environment runs
under the name of orthogonality catastrophe or Fermi edge singularity, is on the basis of the Kondo effect, and we have
worked on extending the techniques to access this physics for various situations over many years. In [1] we have now set
up the approach allowing us to systematically investigate the backaction on the spin as well. This proposed PhD work will
build on these foundations and make the transition to including strongly correlated many-body environments. The goal is
to provide a framework for the characterisation of correlated systems through probing localised spins, which is de facto
an extension of the foundations of NMR to strongly interacting systems in which temporal correlations are as important as
the spatial correlations that alone are addressed in current theories. Through the tremendous progress made in material
design, low temperature physics and quantum control such a theoretical foundation is becoming more and more necessary.
Quantum simulation offers the possibility to create physical phenomena
that are hard to access or control otherwise. Notorious is particularly
many-body physics with strong correlations. Remarkably some types of
such physics can be created in dissipative quantum circuits, in which
the type of correlation physics appears through a nonlinear interaction
of the electron transport with electromagnetic environment
fluctuations. For weakly transmitting conductor such physics is
understood since a long time [1]. But the potential of the quantum
simulation appears only for highly transmitting circuits in which the
transmission time is comparable with the environment's reaction time,
called the dynamical Coulomb blockade regime, for which much less is
known. Although for specific conditions important advances have been
made over the last years [2], recent experimental progress has shown
that there is still much unclear especially when there is strong
backaction of the environment [3]. In this PhD project we will access
this physics through analytical and numerical non-perturbative many-body
modelling, including bosonisation [4] and recently developed
mappings on scattering boundary value problems [5].
[1] G.-L. Ingold and Y. Nazarov, in Single Charge Tunneling ed. by H. Grabert and M. H. Devoret, Ch. 2 (Plenum, 1992).
[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);
A. Anthore, Z. Iftikhar, E. Boulat, F. D. Parmentier, A. Cavanna, A. Ouerghi, U. Gennser, and F. Pierre,
Phys. Rev. X 8, 031075 (2018).
Topological quantum phases have risen to a very active field of research recently,
triggered mostly by the realisation that "ordinary" semiconductor nanostructures
can be fine tuned to exhibit topological properties which are very attractive
for quantum information storing and processing (see also the Research page).
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
[1-6]. 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 [7].
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.
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 [3,4]. 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.
[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).
