Structural and electronic properties of realistic two-dimensional amorphous topological insulators*

Using flat bismuthene as a platform, we systematically constructed realistic amorphous topological insulators systems through ab initio calculations. The radial distribution function shows that the obtained systems have short-range order and lack long-range order. We study the topological properties of these systems by calculating the topological invariants and characterizing the non-trivial topological band structure of our systems. The amorphization tends to suppress the bandgap but does not close it. We find that the survival of the QSH phase through the amorphization process is associated with the SOC strength of the material and the size of the bulk bandgap. Using full ab initio Hamiltonians, we investigate the Landauer conductance of systems with lengths up to 324 nm, comparable with experimental device sizes. We obtain that the topological helical edge states with quantized conductance are preserved inside the gap. For energies outside the topological gap region, we find a strong suppression of the conductance, consistent with Anderson localization. Furthermore, we show how to control the conductance by an exchange field induced by, for instance, suitable substrate proximity or an experimental probe.