PhD projects 2019

Projects available in our group for 2019 are listed below. Please get in touch with Dr Amalia Coldea (amalia.coldea@physics.ox.ac.uk) for further details.
We welcome applications from enthusiastic students who are excited and challenged by understanding the rich novel physical phenomena displayed by novel quantum materials.

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

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

2. Exploring the electronic structure and superconductivity of iron-based superconductors under extreme experimental conditions of high magnetic field, applied pressure and strain

A nematic state is a form of electronic order which breaks the rotational symmetries without changing the translational symmetry of the lattice, and this state may play an important role in understanding high temperature superconductivity. A clear manifestation of a nematic Fermi surface is its strong in-plane anisotropy in transport properties and sensitivity to external parameters, in particular in-plane strain. The resistivity anisotropy is determined by both the electronic structure and the scattering, and the expected Fermi surface deformation give rise naturally to anisotropic electronic properties, whereas the spin-nematic ordering leads to an anisotropy of the electron scattering. This project will consist in magnetotransport studies under strain and pressure to understand the nematic and superconducting states of iron-based superconductors. A suitable candidate needs to have a good understanding of condensed matter physics and good computing skills as well the ability to work well in an experimental team.

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

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

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

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

Details about the application process can be found here and concerning the available scholarships can be found here.