Giant Topological Bandgap and Rashba Effect in Decorated Plumbene: A First-Principles Study

Materials with large Rashba spin splitting (RSS) and quantum spin Hall effect (QSHE) are extremely important in spintronic device applications. Based on first-principles calculations, we present H–Pb–OH, a two-dimensional (2D) hexagonal lattice material capable of achieving complete coexistence of massive RSS and QSHE. The RSS phenomenon (α_R = 3.66 eV Å) in the electronic band of H–Pb–OH occurs when the system’s spatial inversion symmetry is broken and there is an intrinsic electric field present. Furthermore, biaxial stress can modulate the RSS of H–Pb–OH (−8 to 8%). By examining the electronic characteristics of H–Pb–OH, we discover that there is a significant bandgap (1.12 eV) around the Fermi surface, and the system exhibits a topological invariant Z₂ = 1 due to the inversion of the s-p orbitals of the Pb atoms, indicating that H–Pb–OH is a 2D topological insulator with a large topological bandgap. Our findings provide an outstanding candidate material for investigating and implementing the coexistence of RSS and QSHE.