PhD (DPhil) Projects for 2023
1. Intermediate-energy resonant inelastic x-ray scattering as a probe of electronic phenomena driven by strong spin-orbit coupling
At a fundamental level, atomic magnetism originates from the intrinsic spin and the orbital motion of the electrons, which are connected by the spin-orbit coupling (SOC) interaction. This project concerns magnetism in oxides containing heavy metal atoms such as ruthenium, molybdenum and iridium. These atoms have partially filled 4d or 5d electronic orbitals with a very large SOC which strongly entangles the spin and orbital degrees of freedom, resulting in a diverse range of magnetic phenomena as well as the potential for applications in spintronics and energy harvesting.
Resonant inelastic x-ray scattering (RIXS) has emerged as a powerful spectroscopic technique and has been particularly influential in studying phenomena in compounds with strong SOC. In this collaboration with Dr. Ke-Jin Zhou at Beamline I21 in the Diamond Light Source and Prof. Andrew Boothroyd at the University of Oxford, you will investigate strong SOC physics within two research themes. The first concerns excitonic Mott insulators with d4 electronic configuration, e.g., Ru4+ in Ca2RuO4 and Ca3Ru2O7. In the ideal case such d4 ions have a non-magnetic singlet ground state and a triplet excited state with inter-site interactions that create propagating excitations called triplons. The second theme explores ions with the d1 configuration in double perovskites, e.g. Ba2YMoO6, in which the spin and orbital angular momenta are highly entangled leading to strong orbital-dependent exchange and exotic magnetic order.
You will utilise RIXS at the L-edges of transition-metal cations and K-edge of oxygen ligands to probe the low-energy magnetic excitations, the excitonic physics and crystal field splittings, and you will develop models to describe the observed spectra. Candidates are expected to have a good understanding of condensed matter physics and be motivated to develop advanced experimental skills and data modelling.
This project is jointly funded by the Diamond Light Source and Oxford University.
For more information, contact Prof Andrew Boothroyd or Dr Kejin Zhou.
2. Novel Electronic Order and Dynamics in Crystals
Systems of interacting electrons frequently exhibit cooperative electronic order, examples being superconductivity, magnetic order, charge order, and orbital order.
In this project you will explore the basic physics and fundamental mechanisms that drive these different types of order.
The work is particularly motivated by the so-called high-Tc superconductors, which are compounds containing layers of copper and oxygen and exhibit superconductivity in excess of 150 K, and by systems with non-trivial electronic band topology induced by magnetic order These systems represent some of the most important unsolved problems in condensed matter physics.
The principal experimental techniques involved are neutron and magnetic x-ray scattering. These techniques probe structure on the atomic scale by diffraction. Inelastic neutron scattering is used to measure elementary excitations. Your experiments will directly determine the magnetic and electronic ground states and excited states of correlated electron systems, and by doing so you will understand the interactions that stabilise exotic electronic phases. You will also study the bulk properties of materials, such as their magnetic susceptibility, resistivity and heat capacity, using using state-of-the-art facilities in the Clarendon Laboratory.
There is scope for theoretical modelling and numerical analysis to help interpret the data.
For more information, contact Prof Andrew Boothroyd.
National and International Condensed Matter Facilities
These projects offer the exciting opportunity to perform neutron and x-ray scattering experiments at the world's best international facilities, such as those at the Institut Laue-Langevin (ILL) and European Synchrotron Radiation Facility (ESRF) in Grenoble (France), Paul Scherrer Institut near Zürich (Switzerland), DESY synchrotron (Hamburg), and elsewhere, as well as at the ISIS spallation neutron source and Diamond Light Source located at the Rutherford Appleton Laboratory near Oxford. Visits to these facilities provide an excellent opportunity to meet people from other Universities at home and abroad.