Searching for large-gap quantum spin hall insulators: boron-nitride/(Pb, Sn)/α-Al₂O₃ sandwich structures

Topological insulators hold great potential for efficient information processing and storage. Using density functional theory calculations, we predict that a honeycomb lead monolayer can be stabilized on an Al₂O₃ (0001) substrate to become topologically non-trivial with a sizeable band gap (∼0.27 eV). Furthermore, we propose to use a hexagonal boron-nitride (h-BN) monolayer as a protection for the topological states of Pb/Al₂O₃ and Sn/Al₂O₃. Our findings suggest new possibilities for designing and protecting two-dimensional TIs for practical applications.