Magnetism and spin-orbit coupling in thin-film topological materials
A 4 year Eng Doc studentship is available in the Centre for Doctoral Training in Molecular Modelling and Materials Science, UCL (www.m3s.ucl.ac.uk). The studentship will commence in September 2016.
Topological insulators (TIs) are a class of quantum materials that have gapped (insulating) bulk state with gapless and topologically protected surface states. Although these properties were first realised in two dimensional (2D) HgCdTe quantum wells, they are now known to be manifested in a variety of three dimensional (3D) materials, including most prominently a number of Bi allows. TIs have attracted significant attention because of fundamental interest in their novel electronic structure, which arises from strong spin-orbit coupling, as well as potential applications ranging low-power electronics to quantum computing. Developing high quality, thin film TI materials is of significant importance for their incorporation into device structures. Furthermore, if prepared cleanly in ultra-high vacuum, the properties of these materials can be studied with a wide variety of surface-sensitive techniques without exposure to contamination. For example, the structural properties of these films can be characterised by x-ray diffraction while the electronic structure can be mapped with local probes like scanning tunnelling microscopy (STM). There is also substantial interest in studying how the properties of TIs can be modified by the addition of magnetic impurities, since these may, for example, lead to the development of novel ferromagnetic states.
In this studentship project, which will be based in Centre for Doctoral Training Molecular Modelling and Materials Science, UCL , we will combine the thin film growth and structural characterisation expertise of the group of Chris Nicklin (CN) at the Diamond Light Source with the atomic-scale electronic and magnetic characterisation capabilities of the group of Cyrus F. Hirjibehedin (CFH) at UCL to study the properties of bare topological insulators as well as those doped with atomic and molecular magnetic adsorbates. A broad class of TI materials will be prepared by CN’s group in collaboration with other leading UK groups. Particular attention will be paid to the achieving the highest quality intrinsic TI states by tuning, for example, the growth parameters as well as exploring different substrates for the films. After their initial structural characterisation, the most promising candidates will be explored by STM, first at room temperature at Diamond and then at low temperatures and in high magnetic fields at UCL. These latter studies will probe the dispersive behaviour of scattered surface states, and can access both filled and empty states with atomic-level resolution. Furthermore, analysis of the scattering by adsorbed magnetic defects and the development of Landau levels in a magnetic field will provide additional understanding of the topologically non-trivial nature of the material as well as possible evidence for novel quantum phenomena.
Due to funding restrictions, this studentship is only open to applicants from the UK and EU, who have been resident in the UK for at least 3 years preceding their start on the programme or have indefinite leave to remain in the UK.
The candidates should have, or expect to gain, a good honours degree (first or upper second) in a relevant subject, e.g. physics, chemistry, or materials science.
The deadline for applications is 30th March 2016, but the position will be filled as soon as an appropriate candidate is found.