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.

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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

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article

General construction of square-root lattices with arbitrarily degenerate edge states in double bulk gaps

Xin Li, Yu Zhao, Wei Lu, Guanhai Li et al.
Frontiers of Physics
Nonlinear Photonic Systems
article

General construction of square-root lattices with arbitrarily degenerate edge states in double bulk gaps

Xin Li, Yu Zhao, Wei Lu, Guanhai Li, Feilong Yu, Xiaoshuang Chen, Jin Chen
article en

Abstract

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.

Frontiers of PhysicsVol. 22(3)
Shanxi University (CN), ShanghaiTech University (CN), Shanghai Institute of Technical Physics (CN), University of Chinese Academy of Sciences (CN)
National Natural Science Foundation of China, China Postdoctoral Science Foundation
Sustainable cities and communities
Openalex Percentile: Top 10%
Nonlinear Photonic Systems
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General construction of square-root lattices with arbitrarily degenerate edge states in double bulk gaps — Xin Li, Yu Zhao, et al. · Frontiers of Physics (2026) | TGRS Research Map | TGRS