Quantum spin Hall edge transport in two-dimensional transition-metal dichalcogenides depends on whether their one-dimensional 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 1T′/2H WSe2 heterostructures. Edge-projected spectra reveal robust edge states in 1T′ ribbons; and these states remain robust against a laterally infinite 2H substrate, which only shifts the Dirac point via long-wavelength corrugation without introducing additional in-gap states. By contrast, terminated 2H 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 1T′-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 2H edges -- for achieving quantized conductance and unambiguous spectroscopic
@article{arxiv.2508.12841,
title = {Edge-state competition in a 2D topological insulator-semiconductor heterostructure},
author = {Wei Li and Pier Philipsen and Thomas Brumme and Thomas Heine},
journal= {arXiv preprint arXiv:2508.12841},
year = {2025}
}