Exploring a new topological insulator in β-BiAs oxide.

The scarcity of suitable quantum spin Hall (QSH) insulators with a significant bulk gap poses a major challenge to the widespread application of the QSH effect. This study employs first-principles calculations to investigate the stability, electronic structure, and topological properties of a fully oxygenated bismuth arsenide system. Without the influence of spin-orbit coupling (SOC), the valence and conduction bands at the Γ-point exhibit a semimetallic nature. However, introducing SOC leads to a substantial 352 meV band gap, which allows operation at room temperature. The calculation of the topological invariant reveals , and the presence of topologically protected edge states in a Dirac cone at the Γ point confirms the existence of a non-trivial topological state. The epitaxial growth of β-BiAsO2 on a SiO2 substrate maintains the band topology of β-BiAsO2, spin lock with SOC effect. Additionally, the fully oxidized surfaces of β-BiAsO2 are inherently resistant to surface oxidation and degradation, suggesting a promising approach for developing room-temperature topological quantum devices. These findings not only introduce new vitality into the 2D group-VA materials family and enrich the available candidate materials in this field but also highlight the potential of these 2D semiconductors as appealing ultrathin materials for future flexible electronics and optoelectronics devices.