Edge-state competition in a 2D topological insulator-semiconductor heterostructure

TL;DR

This study investigates the robustness of quantum spin Hall edge states in 2D WSe$_2$ heterostructures, showing how substrate interactions and edge terminations influence topological properties and electronic behavior.

Contribution

It demonstrates the preservation of topological edge states in 1T' WSe$_2$ ribbons on 2H substrates and analyzes how twist angles and edge terminations affect electronic structure and miniband formation.

Findings

Robust edge states persist on 2H substrates without additional in-gap states.

Terminated 2H edges generate trivial dispersion branches that weakly hybridize with topological modes.

Lattice relaxation and twist angles significantly influence miniband reconstruction and layer decoupling.

Abstract

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 WSe$_2$ 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