Epitaxial Growth of Ultraflat Bismuthene with Large Topological Band Inversion Enabled by Substrate-Orbital-Filtering Effect

TL;DR

This paper demonstrates a method to create large-gap quantum spin Hall systems using substrate-orbital-filtering effects, exemplified by epitaxial bismuthene on Ag(111), revealing large topological gaps suitable for practical applications.

Contribution

It introduces a novel substrate-orbital-filtering strategy to engineer large-gap QSH materials, validated by experimental synthesis and theoretical analysis.

Findings

Large topological gap of ~1 eV at the K point.

Selective filtering of Bi pz orbitals by substrate.

Identification of topological edge states via spectroscopy.

Abstract

Quantum spin Hall (QSH) systems hold promises of low-power-consuming spintronic devices, yet their practical applications are extremely impeded by the small energy gaps. Fabricating QSH materials with large gaps, especially under the guidance of design principles, is essential for both scientific research and practical applications. Here, we demonstrate that large on-site atomic spin-orbit coupling can be directly exploited via the intriguing substrate-orbital-filtering effect to generate large-gap QSH systems and experimentally realized on the epitaxially synthesized ultraflat bismuthene on Ag(111). Theoretical calculations reveal that the underlying substrate selectively filters Bi pz orbitals away from the Fermi level, leading pxy orbitals with nonzero magnetic quantum numbers, resulting in large topological gap of ~1 eV at the K point. The corresponding topological edge states are identified through scanning tunneling spectroscopy combined with density functional theory calculations. Our findings provide general strategies to design large-gap QSH systems and further explore their topology-related physics.