Engineering quantum phases in two dimensions via vacancy-induced electronic reconstruction

Topological phases of matter are commonly understood as emerging from crystalline symmetry and intrinsic spin-orbit coupling or, less frequently, from disorder-driven electronic renormalization. In realistic materials, however, structural defects naturally combine both ingredients. Here, we propose a universal mechanism by which atomic vacancies drive a topological phase transitions in two-dimensional semiconductors through electronic reconstruction. We show that vacancies generate locally ordered dangling-bond states governed by well-defined hopping and spin-orbit interactions, while their spatial distribution and mutual coupling introduce long-range disorder. As vacancy concentration increases, the hybridization of these defect states forms an emergent electronic subspace that undergoes a topological transition. By combining large-scale density functional theory calculations with an interpretable orbital based Hamiltonian, we find that this vacancy-induced electronic reconstruction can stabilize quantum spin Hall, quantum anomalous Hall, and Weyl semimetal phases. Our results indicate vacancies not as detrimental perturbations, but as active design elements capable of transforming trivial insulators into topological quantum matter, providing realistic routes for defect-engineered topological devices. Topological phases of matter typically arise from crystalline symmetry and spin–orbit coupling, but structural defects in materials can also play a crucial role. Here, the authors demonstrate that atomic vacancies in two-dimensional semiconductors can induce topological phase transitions, suggesting vacancies as transformative elements for designing defect-engineered topological devices.