A piezoelectric quantum spin Hall insulator VCClBr monolayer with a pure out-of-plane piezoelectric response

The combination of piezoelectricity with a nontrivial topological insulating phase in two-dimensional (2D) systems, namely piezoelectric quantum spin Hall insulators (PQSHI), is intriguing for exploring novel topological states toward the development of high-speed and dissipationless electronic devices.