Photonic axion insulator
Axions, hypothetical elementary particles that remain undetectable in nature, can arise as quasiparticles in three-dimensional crystals known as axion insulators. Previous implementations of axion insulators have largely been limited to two-dimensional systems, leaving their topological properties in three dimensions unexplored in experiment. Here, we realize an axion insulator in a three-dimensional photonic crystal and probe its topological properties. Demonstrated features include half-quantized Chern numbers on each surface that resembles a fractional Chern insulator, unidirectional chiral hinge states forming topological transport in three dimensions, and arithmetic operations between fractional and integer Chern numbers. Our work experimentally establishes the axion insulator as a three-dimensional topological phase of matter and enables chiral states to form complex, unidirectional three-dimensional networks through braiding.
Authors
- Subhaskar Mandal (ORCID: https://orcid.org/0000-0002-3202-9364)
- Maia G. Vergniory (ORCID: https://orcid.org/0000-0001-7336-3062)
- Yan Meng (ORCID: https://orcid.org/0000-0002-1387-1644)
- Chiara Devescovi (ORCID: https://orcid.org/0000-0003-2321-6421)
- Gui-Geng Liu (ORCID: https://orcid.org/0000-0003-4328-9142)
- Zhen Gao (ORCID: https://orcid.org/0000-0001-8284-7958)
- Baile Zhang (ORCID: https://orcid.org/0000-0003-1673-5901)
- Qiang Wang (ORCID: https://orcid.org/0000-0003-3407-6444)
- Y. D. Chong (ORCID: https://orcid.org/0000-0002-8649-7884)
- Yang Long (ORCID: https://orcid.org/0000-0001-7600-3396)
- Linyun Yang (ORCID: https://orcid.org/0000-0001-8079-5779)
- Ziyao Wang (ORCID: https://orcid.org/0009-0006-1122-268X)
- Peiheng Zhou (ORCID: https://orcid.org/0000-0002-1905-7758)
- Rimi Banerjee (ORCID: https://orcid.org/0000-0001-5840-2756)
- Xiang Xi (ORCID: https://orcid.org/0000-0002-4715-4352)
- Aitzol García‐Etxarri (ORCID: https://orcid.org/0000-0002-5867-2390)
- Antonio Morales-Pérez (ORCID: https://orcid.org/0000-0002-1482-6407)
Institutions
- Ikerbasque (ES)
- Université de Sherbrooke (CA)
- University of Electronic Science and Technology of China (CN)
- University of the Basque Country (ES)
- Nanyang Technological University (SG)
- Dongguan University of Technology (CN)
- Southern University of Science and Technology (CN)
- Westlake University (CN)
- ETH Zurich (CH)
- Max Planck Institute for Chemical Physics of Solids (DE)
- National Engineering Research Center of Electromagnetic Radiation Control Materials (CN)
- Collaborative Innovation Center of Advanced Microstructures (CN)
- Donostia International Physics Center (ES)
- Nanjing University (CN)
Publication Details
- Journal
- Science
- Published
- 2025-01-09
- DOI
- https://doi.org/10.1126/science.adr5234
- Citations
- 28
- Primary Topic
- Topological Materials and Phenomena
- Type
- article
- Field-Weighted Citation Impact
- 34.91