General construction of square-root lattices with arbitrarily degenerate edge states in double bulk gaps
Square-root topological insulators can inherit edge states from an underlying topological parent system, but existing realizations are typically limited to low degeneracy and small winding numbers. Here, we introduce a general design strategy for extending square-root topological phases to an arbitrary winding number N by combining a fixed structural-subdivision framework with long-range couplings, enabling the number of inherited edge states to increase systematically without raising the root order. We reveal a parity-dependent winding-number phase diagram, where odd and even maximum winding numbers exhibit distinct phase-boundary structures and topological transition sequences. The resulting square-root lattices host N-fold degenerate topological edge states within each of two bulk band gaps, with the corresponding modes exhibiting characteristic fixed-position spatial localization. We also discuss experimentally accessible implementations in photonic waveguide arrays and topolectrical circuits. Our approach provides a scalable route to highly degenerate topological modes and multi-gap wave control in artificial lattices.
Authors
- Xin Li (ORCID: https://orcid.org/0000-0002-2587-7883)
- Yu Zhao
- Wei Lu
- Guanhai Li
- Feilong Yu
- Xiaoshuang Chen
- Jin Chen
Institutions
- Shanxi University (CN)
- ShanghaiTech University (CN)
- Shanghai Institute of Technical Physics (CN)
- University of Chinese Academy of Sciences (CN)
Publication Details
- Journal
- Frontiers of Physics
- Published
- 2026-09-16
- DOI
- https://doi.org/10.15302/frontphys.2027.035201
- Primary Topic
- Nonlinear Photonic Systems
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- National Natural Science Foundation of China
- China Postdoctoral Science Foundation