ABSTRACT: Since the discovery of graphene, 2D materials, such as 2D Dirac and topological materials, have attracted tremendous interest because they offer a new platform for next-generation of electronic, optoelectronic, spintronic and valleytronic devices with distinctive properties different from their 3D bulk counterparts. Most 2D materials are theoretically predicted in the freestanding form. But the freestanding 2D atomic layers are generally metastable and their intrinsic properties may be altered when they are transferred onto a substrate, which is often required for measurement as well as for eventual device fabrication. In this talk, I will present our recent studies to explore a novel approach of surface-based 2D Dirac and topological materials by direct epitaxial growth of metal overlayers on a semiconductor substrate without transfer process, using first-principles calculation combined with tight-binding model analysis. Specifically, I will discuss several examples demonstrating formation Dirac, quantum spin Hall and quantum anomalous Hall states in the Si(111) surface. Furthermore, I will discuss an interesting approach to manipulate edge spin current of a quantum spin Hall insulator by bending strain engineering. Our findings may greatly broaden the scientific scope and technological impact of emerging Dirac and topological materials.
BIOGRAPHY: Prof. Liu Research Group Webpage.