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

Abstract

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 ∼0.3 eV via a <i>selective</i> substrate-orbital-filtering effect. Tight-binding model analyses show the <i>p</i>_<i>z</i> orbital in half of the Pb overlayer is selectively removed by the BaTe substrate, leaving behind a <i>p</i>_<i>z</i>-<i>p</i>_{<i>x</i>,<i>y</i>} band inversion. Based on the same working principle, the gap can be further increased to ∼0.5-0.6 eV by surface adsorption of H or halogen atoms that filters out the other half of the Pb <i>p</i>_<i>z</i> orbitals. The mechanism of <i>selective</i> 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.