Edge‐State Competition in a 2D Topological Insulator‐Semiconductor Heterostructure

ABSTRACT Quantum spin Hall edge transport in 2D transition‐metal dichalcogenides depends on whether their 1D edge channels are preserved under realistic substrates and device boundaries. Here we implement spin‐orbit coupling in DFTB and GFN‐xTB within the Amsterdam Modeling Suite, and apply it to heterostructures. Edge‐projected spectra reveal robust edge states in ribbons; these states remain robust against a laterally infinite H substrate, which only shifts the Dirac point via long‐wavelength corrugation without introducing additional in‐gap states. By contrast, terminated H edges generate trivial dispersion branches in the same energy window that hybridize only weakly with the topological edge modes. In the bulk, Fermi‐level states are ‐derived; at the small twist angle, lattice‐relaxation‐induced strain drives miniband reconstruction, whereas at the large twist angle, the layers become electronically decoupled. These findings suggest the conditions – controlled twist angle and avoidance of terminated H edges – for achieving quantized conductance and unambiguous spectroscopic detection of helical edges.