Engineering Quantum Phases in Two Dimensions via Vacancy-Induced Electronic Reconstruction

TL;DR

This paper presents a universal mechanism where atomic vacancies in two-dimensional semiconductors induce topological phase transitions, enabling the transformation of trivial insulators into various topological quantum phases.

Contribution

It introduces a defect-engineering approach using vacancies to induce and control topological phases in 2D materials, supported by theoretical and computational analysis.

Findings

Vacancies generate localized states with specific hopping and spin-orbit interactions.

Increasing vacancy concentration leads to a topological transition in the electronic structure.

Vacancy-induced states can stabilize quantum spin Hall, quantum anomalous Hall, and Weyl semimetal phases.

Abstract

Topological phases of matter are commonly understood as emerging either from crystalline symmetry and intrinsic spin-orbit coupling or from disorder-driven electronic renormalization. In realistic materials, however, structural defects naturally combine both ingredients. Here, we demonstrate a general and material-independent mechanism by which atomic vacancies can induce topological phase transitions in two-dimensional semiconductors that are otherwise topologically trivial. 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. Using a tight-binding framework supported by large-scale density functional theory calculations, we show that this vacancy-induced electronic reconstruction can robustly stabilize quantum spin Hall, quantum anomalous Hall, and Weyl semimetal phases, depending on symmetry breaking and spin polarization. Our results establish vacancies not merely as perturbations, but as active design elements capable of transforming trivial insulators into topological quantum matter, opening realistic routes for defect-engineered topological devices.