Topological insulator plasmonics

Topological insulators (TIs) are a new type of material that has recently been discovered. They have highly conductive surface states, while their bulk remains insulating. Because of extremely strong spin-orbit coupling in these materials, surface electrons have a spin-momentum locking texture, so that they are almost free from scattering, known as topological protection. The electrons are also massless Dirac particles similar to those in graphene, even at room temperature. While most work to-date has been 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. These have predicted exotic light-matter interactions between the surface electrons in the TI and photons. Because the topologically protected carriers are confined to the surface of the material, by controlling the physical shape of the material on the nanometer scale the material interaction with light can be controlled. These interactions represent a new type of light-matter phenomena and could lead to applications in sensor technology, optical coatings and new laser technologies. The predicted interactions are strongest in the terahertz (THz) region of the spectrum that lies between the microware and infrared. It has traditionally been difficult to access this part of the spectrum, however, the UoL is a leader in this field and has a number of state-of-the-art THz laboratories. The THz region is ideal for this type of research because modern femtosecond lasers and nanofabrication technology are able to access timescales and length scales well below those of terahertz waves leading to very precise measurement and control of the electromagnetic field. This project will explore the interaction between THz light and TI nanostructured materials and will be based in the Bragg centre. The topological thin films will be grown using the recently commissioned Royce-funded multi-deposition chamber. 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/supercondutor). Sample characterization will be carried out by a range of techniques available in the Bragg centre, 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 THz laboratories. This project aims to identify exotic light-matter interactions such as the topological surface plasmon-polariton that have been theoretically predicted. These new types of excitations will be of interest to both scientific researchers and applications.