Braiding topology of symmetry-protected degeneracy points in non-Hermitian systems

Abstract

Degeneracy points in non-Hermitian systems are of great interest. While a homotopic framework exists for understanding their behavior in the absence of symmetry, it does not apply to symmetry-protected degeneracy points with reduced codimension. In this work, utilizing algebraic topology, we provide a systematic classification of these symmetry-protected degenerate points and investigate the braid conservation rule followed by them. Using a model Hamiltonian and circuit simulation, we discover that, contrary to simple annihilation, pairwise-created symmetry-protected degeneracy points merge into a higher-order degeneracy point, which goes beyond the abelian picture. Our findings empower researchers across diverse fields to uncover new phenomena and applications harnessing symmetry-protected non-Hermitian degeneracy points.

17 pages, 7 figures

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Cited by in corpus (5)

• Homotopy, Symmetry, and Non-Hermitian Band Topology
• Braiding Topology of Non-Hermitian Open-Boundary Bands
• Observation of Braid-Protected Unpaired Exceptional Points
• Recent advances in the combination of nonlinearity and exceptional points
• Compound symmetries and double antisymmetry groups in linear time-invariant photonic systems