Atomically-thin layers of two-dimensional materials can be assembled in vertical stacks (called ‘heterostructures’), which are held together by relatively weak van der Waals forces, allowing for coupling between monolayer crystals with incommensurate lattices and arbitrary mutual rotation, or ‘twist’. The twist is a new degree of freedom recently discovered in 2D materials and now widely used in the design of 2D heterostructures. It leads to a new in-plane periodicity in the local atomic registry of the constituent crystal structures, known as a moiré superlattice. The moiré superlattice has a dramatic effect on the motion of electrons in the plane of the 2D structure. For example, when two monolayers of graphene are attached to each other with a ‘magic twist angle’ a superconductor-insulator transition is observed. Similarly, in 2D semiconductors, the twist has been shown to lead to a variety of unusual optical phenomena as we reported in our recent work in Nature (https://www.nature.com/articles/s41586-019-0986-9). In this project, this new degree of freedom will be explored in a variety of layered materials and new phenomena and physics will be sought.
You will join an energetic team of 4 PhD students and 3 postdocs. You will work on novel device fabrication in the modern clean room, and will carry out a large number of optical experiments in the state-of-the-art laboratories of the Sheffield group. You will further collaborate with leading groups around the world on physics and technology of 2D materials and nano-photonics. We work closely with the leading groups in many related research fields, including 2D materials (National Graphene Institute, Manchester), nano-photonics and materials (Imperial College London), and optical spectroscopy (Technical University Dortmund) and many others, and visits to their experimental facilities will be possible and encouraged. See further details at http://ldsd.group.shef.ac.uk/research/2d-materials/
Science Graduate School: As a PhD student in one of the science departments at the University of Sheffield, you’ll be part of the Science Graduate School – a community of postgraduate researchers working across biology, chemistry, physics, mathematics and psychology. You’ll get access to training opportunities designed to support your career development by helping you gain professional skills that are essential in all areas of science. You’ll be able to learn how to recognise good research and research behaviour, improve your communication abilities and experience technologies that are used in academia, industry and many related careers. Visit http://www.sheffield.ac.uk/sgs to learn more.