Universal Vacancy-Driven Topological Transitions in 2D Materials

We unveil a universal mechanism by which atomic vacancies drive topological phase transitions in two-dimensional semiconductors. Using a combination of tight-binding models and high-throughput ab initio calculations on 308 candidate materials from the C2DB database, we show that vacancy-induced dangling-bond states near the Fermi level provide the minimal ingredients for quantum spin Hall and quantum anomalous Hall phases. The interplay between intra- and inter-vacancy interactions leads to band inversion and topological gap opening, tunable by vacancy concentration and spin–orbit strength. Exemplified in AgI and GeS₂, this vacancy-driven topology establishes a general route to engineer robust topological states in experimentally accessible 2D semiconductors.