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Bismuthene and related systems: a new class of 2D topological insulators

Summary

Quantum spin Hall (QSH) phases have been predicted for 2D honeycomb materials, with anticipated potential for spintronic applications based on their conductive helical edge states. Yet, a large bulk band gap driven by spin-orbit coupling is instrumental. In this spirit, in the first funding period the applicants have successfully demonstrated the synthesis of a 2D QSH candidate system based on the highest-Z element bismuth. A bismuthene monolayer has been stabilized on a SiC substrate, with a large bulk gap of 0.8 eV and highly confined metallic edge channels. The present project will focus on the manipulation and control of the topological edge states, and will comprise a systematic spectroscopic study of the bulk and edge states by scanning tunneling microscopy/spectroscopy (STM/STS) as well as angle-resolved photoemission (ARPES). The overarching goal is to study the response of the helical edge states to intentional perturbations, which include, e.g., external fields, impurity atoms or special geometric situations such as quantum interference at domain boundaries. Key effects on the electronic edge state spectrum such as inducing an energy gap by breaking time- reversal symmetry (TRS) are fundamentally relevant to the ability to switch the conduction channel.

Fabrication of bismuthene device structures for transport measurements – where QSH conductance quantization may be expected up to room temperature – will be addressed by applying technologies for film passivation with suitable coatings and by nanopatterning techniques. The program will also address the synthesis of related group V systems such as antimonene and arsenene on insulating substrates and the corresponding electronic and topological properties.