Functionalized Bismuth Films: Giant Gap Quantum Spin Hall and Valley-Polarized Quantum Anomalous Hall States

TL;DR

This study predicts large band gap quantum spin Hall and quantum anomalous Hall states in hydrogen-decorated bismuth films, revealing their potential for room-temperature applications and intrinsic valley polarization.

Contribution

First principles calculations demonstrate giant band gaps in H-decorated Bi films, introducing a new pathway for room-temperature topological insulators with valley-polarized QAH states.

Findings

Band gaps up to 1.01 eV (QSH) and 0.35 eV (QAH) predicted.

QAH state exhibits valley-polarized quantum anomalous Hall effect.

Large spin-orbit interaction and hydrogen decoration are key factors.

Abstract

The search for new large band gap quantum spin Hall (QSH) and quantum anomalous Hall (QAH) insulators is critical for their realistic applications at room temperature. Here we predict, based on first principles calculations, that the band gap of QSH and QAH states can be as large as 1.01 eV and 0.35 eV in an H-decorated Bi(111) film. The origin of this giant band gap lies both in the large spin-orbit interaction of Bi and the H-mediated exceptional electronic and structural properties. Moreover, we find that the QAH state also possesses the properties of quantum valley Hall state, thus intrinsically realising the so-called valley-polarized QAH effect. We further investigate the realization of large gap QSH and QAH states in an H-decorated Bi(\={1}10) film and X-decorated (X=F, Cl, Br, and I) Bi(111) films.