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Chiral edge-state signatures of Berry monopole merging and splitting in a bilayer photonic crystal slab with synthetic momentum

Ngoc Duc Le1,2,3,*, D.-H.-Minh Nguyen1,4,†, Dung Xuan Nguyen5,6,‡, Hai Son Nguyen7,8,9,§, and Dario Bercioux1,10,∥

  • *Contact author: lnduc@iop.vast.vn
  • †Contact author: d.h.minh.ng@gmail.com
  • ‡Contact author: dungmuop@gmail.com
  • §Contact author: hai-son.nguyen@ec-lyon.fr
  • ∥Contact author: dario.bercioux@dipc.org
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Phys. Rev. Research 8, 033338 – Published 21 September, 2026

DOI: https://doi.org/10.1103/6ync-5qb9

Abstract

Berry monopoles are point degeneracies in parameter space where the Berry curvature emanates radially, analogous to magnetic monopoles. Here, we report the adiabatic merging and splitting of Berry monopoles in a bilayer photonic crystal slab combining one genuine and one synthetic momentum. Two monopoles approach, merge, and split within this hybrid parameter space. The process is described by an effective coupled-mode model and confirmed by full-wave simulations. We further propose a scheme to experimentally probe the Berry monopole merging and splitting by monitoring the evolution of chiral edge states localized at the interface between two topological phases with inverted band structures.

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Phys. Rev. Research 8, 033338– Published 21 September, 2026
  • Received 24 July 2025
  • Accepted 30 August 2026
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