Selective Substrate-Orbital-Filtering Effect to Realize the Large-Gap Quantum Spin Hall Effect

Although Pb harbors a strong spin-orbit coupling effect, pristine plumbene (the last group-IV cousin of graphene) hosts topologically trivial states. Based on first-principles calculations, we demonstrate that epitaxial growth of plumbene on the BaTe(111) surface converts the trivial Pb lattice into a quantum spin Hall (QSH) phase with a large gap of similar to 0.3 eV via a selective substrate-orbital-filtering effect. Tight-binding model analyses show the p(z) orbital in half of the Pb overlayer is selectively removed by the BaTe substrate, leaving behind a p(z)-p(x,y) band inversion. Based on the same working principle, the gap can be further increased to similar to 0.5-0.6 eV by surface adsorption of H or halogen atoms that filters out the other half of the Pb p(z) orbitals. The mechanism of selective substrate-orbital-filtering is general, opening an avenue to explore large-gap QSH insulators in heavy-metal-based materials. It is worth noting that plumbene has already been widely grown on various substrates experimentally.

Automated summary

The study shows that epitaxial growth of plumbene on the BaTe(111) surface can transform the trivial Pb lattice into a quantum spin Hall (QSH) phase with a large gap. Surface adsorption of H or halogen atoms can further increase the gap, demonstrating the potential for exploring large-gap QSH insulators in heavy-metal-based materials.