Elucidating the Surface Properties of Sr₃PbO Inverse-Perovskite Topological Insulator: A First-Principles Study

The emergence of robust surface electronic states in topological insulators such as bulk Sr₃PbO inverse-perovskite makes them suitable candidates for spintronic devices and solid-state quantum computers. Herein, the atomic structure, surface energetics, and electronic properties of Sr₃PbO inverse-perovskite Sr₂O (SO)-terminated and SrPb-terminated (001) surfaces are examined using density functional theory. A comparison of the computed structural properties of SO-termianted and SrPb-terminated (001) surfaces reveals maximum surface rumpling and changes in interlayer distances for the SrPb-terminated surface of Sr₃PbO. However, the calculated surface energies indicate that both SO-termianted and SrPb-terminated (001) surfaces of Sr₃PbO are energetically feasible, indicating that these surfaces can coexist in a polycrystalline sample of this material. Due to the presence of Pb in Sr₃PbO, a comprehensive examination of the electronic structure of bulk and supercell slab structures of Sr₃PbO by taking spin–orbit coupling effects into consideration is conducted. Noninsulating nature of electronic structure for the two possible (001) terminations of Sr₃PbO is found. The domination of Pb-6p states at the Fermi energy and the hole screening observed at the SrPb-terminated surface of Sr₃PbO support the p-type nature observed in the experiment.