Topological electronic structure and spin texture of quasi-one-dimensional higher-order topological insulator Bi4Br4

Journal article

Abstract The notion of topological insulators (TIs), characterized by an insulating bulk and conducting topological surface states, can be extended to higher-order topological insulators (HOTIs) hosting gapless modes localized at the boundaries of two or more dimensions lower than the insulating bulk. In this work, by performing high-resolution angle-resolved photoemission spectroscopy (ARPES) measurements with submicron spatial and spin resolution, we systematically investigate the electronic structure and spin texture of quasi-one-dimensional (1D) HOTI candidate Bi 4 Br 4 . In contrast to the bulk-state-dominant spectra on the (001) surface, we observe gapped surface states on the (100) surface, whose dispersion and spin-polarization agree well with our ab-initio calculations. Moreover, we reveal in-gap states connecting the surface valence and conduction bands, which is a signature of the hinge states inside the (100) surface gap. Our findings provide compelling evidence for the HOTI phase of Bi 4 Br 4 . The identification of the higher-order topological phase promises applications based on 1D spin-momentum locked current in electronic and spintronic devices.

Authors: Zhao, W; Yang, M; Xu, R; Du, X; Zhai, K

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Nature Research
• Journal: Nature Communications
• Volume: 14
• Issue: 1
• Pages: 8089-8089
• Article number: 8089
• Publication date: 2023-12-07
• DOI: 10.1038/s41467-023-43882-z
• EISSN: 2041-1723
• ISSN: 2041-1723
• Language: English
• Keywords: Topological order; Angle-resolved photoemission spectroscopy; Topological insulator; Spectral line; Topology (electrical circuits); Surface states; Condensed matter physics; Photoemission spectroscopy; Ferromagnetism; Materials science; Quantum mechanics; Electronic structure; Surface (topology); Spintronics; Physics