TOPCHEM · Topological Chemistry in Ternary Compunds

The discovery of topological insulators has ignited intensive research activity in condensed matter and materials science. However, the understanding of topological electronic structure from a chemical view is still deficient.This action proposes the investigation of novel ternary ABC topological insulators (A: alkali, alkaline earth, rare earth, Group 11, B: alkaline earth or Group 8-12, C: main group element) by focusing on three aspects: 1) growth of high-quality single crystals; 2) structural characterisation and relation between topological electronic structure and chemical concepts; 3) manipulation of electronic structure aiming at thermoelectric applications.First, high-quality ABC single crystals with selected composition will be grown by suitable methods. The Fermi level will be tuned by chemical doping or controlling the intrinsic defects to observe the topological physics. Subsequently, a detailed bulk and surface structural characterisation will be performed. The electronic structure of a material in the reciprocal space can be linked to chemical concepts in real space, such as chemical bonding, electronegativity differences, orbital overlap, etc. A systematic study of the crystalline bulk and surface structures will be performed by Synchrotron and low energy electron diffraction, and X-ray absorption near the edge, to find the relation between chemical concepts and the electronic structure of selected topological materials.Finally, based on the understanding of the relation between chemical concepts and electronic structure, the thermoelectric transport properties of these novel ABC topological insulators will be investigated and optimised for thermoelectric applications.The implementation of this project will deepen the understanding of topological chemistry and stimulate the technological application of topological materials. It will contribute to EU Horizon 2020 goals creating a single market for knowledge, research, and innovation.