Topological phase transition in quasi-one-dimensional bismuth iodide Bi 4 I 4

Journal article

Quasi-one-dimensional (quasi-1D) bismuth iodide Bi4I4 exhibits versatile topological phases of matter including weak topological insulator (WTI) and higher-order topological insulator (HOTI) phases with high tunability in response to external parameters. In this work, performing laser-based angle-resolved photoemission spectroscopy with submicron spatial resolution (micro-ARPES), we reveal the presence of an energy gap on the (100) surface of the low-temperature α-Bi4I4, providing spectroscopic evidence for the HOTI phase. Conversely, the high-temperature β-Bi4I4 harbors gapless Dirac fermions on the (100) surface alongside gapped states on the (001) surface, thereby establishing a WTI phase. By tracking the temperature evolution of the (100) surface states, we unveil a thermal hysteresis of the surface gap in line with the α-β structural phase transition. Our findings directly evidence a temperature-induced topological phase transition from WTI to HOTI in Bi4I4, which paves the way to its potential applications at room temperature.

Authors: Zhao, WX; Yang, M; Du, X; Li, YD; Zhai, KY

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Nature Research
• Journal: npj Quantum Materials
• Volume: 9
• Issue: 1
• Article number: 103
• Publication date: 2024-12-20
• Acceptance date: 2024-11-19
• DOI: 10.1038/s41535-024-00711-w
• EISSN: 2397-4648
• Language: English