Large-gap quantum anomalous Hall states induced by functionalizing buckled Bi-III monolayer/Al\(_{2}\)O\(_{3}\)

• Published in: arXiv.org
• Main Authors: Jin, Suhua, Xia, Yunyouyou, Shi, Wujun, Hu, Jiayu, Claessen, Ralph, Hanke, Werner, Thomale, Ronny, Li, Gang
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 02.08.2022
• Subjects: First principles; Monolayers; Operating temperature; Orbitals; Phase transitions; Physics - Materials Science; Physics - Mesoscale and Nanoscale Physics; Quantum Hall effect; Spin exchange; Spintronics; Substrates; Topology; Zeeman effect
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2208.01438

Chiral edge modes inherent to the topological quantum anomalous Hall (QAH) effect are a pivotal topic of contemporary condensed matter research aiming at future quantum technology and application in spintronics. A large topological gap is vital to protecting against thermal fluctuations and thus enabling a higher operating temperature. From first-principle calculations, we propose Al\(_{2}\)O\(_{3}\) as an ideal substrate for atomic monolayers consisting of Bi and group-III elements, in which a large-gap quantum spin Hall effect can be realized. Additional half-passivation with nitrogen then suggests a topological phase transition to a large-gap QAH insulator. By effective tight-binding modelling, we demonstrate that Bi-III monolayer/Al\(_{2}\)O\(_{3}\) is dominated by \(p_{x}, p_{y}\) orbitals, with subdominant \(p_z\) orbital contributions. The topological phase transition into the QAH is induced by Zeeman splitting, where the off-diagonal spin exchange does not play a significant role. The effective model analysis promises utility far beyond Bi-III monolayer/Al\(_{2}\)O\(_{3}\), as it should generically apply to systems dominated by \(p_{x}, p_{y}\) orbitals with a band inversion at \(\Gamma\).