Novel 2D Materials: Functionalized Stanene and Bismuthene Honeycomb Lattices

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This project is aimed at realizing and tuning the topological phases of honeycomb lattices, i.e. of Graphene analogs, built from high-Z atoms. We focus on honeycombs of Sn and Bi atoms (Stanene, Bismuthene). These are theoretically described as wide-gap Quantum Spin Hall (QSH) systems, suitable for room temperature applications. Addressing the practical realization, we have identified SiC(0001) as a suitable substrate. Our epitaxial experiments have already succeeded in producing Sn and Bi honeycomb layers, characterized by scanning tunneling microscopy (STM). The project will explore the effect of functionalization on the electronic and topological properties. This includes buffer layers below the honeycomb layer, as well as surface functionalization with, e.g., metal or halogen atoms. Intriguingly, decoration with hydrogen atoms or magnetic impurities is expected to create the Quantum Anomalous Hall (QAH) effect. The topological properties will be probed by scanning tunneling spectroscopy (STS) of the 1D edge channels. The band structure is accessed by angle-resolved photoemission (ARPES). Our epitaxy technology thus provides access to a novel class of QSH materials, available for exchange in the SPP 1666 Priority Program. It will profit from close collaboration with many other projects, reaching from density functional theory to synchrotron-based methods, optical spectroscopy techniques, and projects addressing the transport properties.