Topological insulators (TIs) are a recently discovered new type of material. Although their bulk is insulating, they have highly conductive surface states that are almost free from scattering even at room temperature, through a process known as topological protection. These conducting electrons are massless Dirac particles, similar to those in graphene.
While most work to date has focused on the use of TIs in electronic devices, there have recently been exciting theoretical proposals of how this new type of material interacts with light and other types of radiation. Exotic light-matter interactions are predicted between the surface electrons and photons. Because the topologically protected carriers are confined to the material surface, by controlling the physical shape of the material on the nanometre scale, the material interaction with light can also be controlled. These interactions represent a new type of light-matter phenomenon and could lead to applications in sensor technology, optical coatings and new laser technologies.
The predicted interactions are strongest in the terahertz (THz) frequency region of the spectrum that lies between the microware and infrared regions. It has traditionally been difficult to access this part of the spectrum. However, the University of Leeds is an international leader in this field and has a number of state-of-the-art THz laboratories.
This project will explore the interaction between THz radiation and TI nanostructured materials. The topological thin films will be grown using the recently commissioned multi-deposition apparatus at Leeds, funded by the UK Henry Royce Institute. The TI materials that will be studied are Bi2Se3, (Bi1-xSbx)2Te3 and TI-based heterostructures (e.g. TI p-n junction, TI/magnetic thin film or TI/superconductor). Sample characterization will be carried out by a range of techniques available in the University’s Bragg Centre for Materials Research, including XRD, EDX, SEM and magnetoelectric transport measurements. The device fabrication will be carried out in the state-of-the-art nanofabrication facilities available in the nanotechnology cleanroom and measured in the School’s THz laboratories.
This project aims to identify exotic light-matter interactions such as the ‘topological surface plasmon polariton’ that have been theoretically predicted. Demonstration of these new types of excitations and interactions will not only be of interest to scientific researchers but open the way to a number of potential applications.
This project would suit an applicant with a good first degree in Physics, Electronic Engineering, or an aligned subject, with a strong interest in condensed matter physics.