Experimental realization of a Weyl exceptional ring

By Alexander Cerjan, Sheng Huang, Mohan Wang, Kevin P. Chen, Y. Chong, M. Rechtsman. Nature Photonics, 2018

332 citations recorded by the source corpus.

Weyl points are isolated degeneracies in reciprocal space that are monopoles of the Berry curvature. This topological charge makes them inherently robust to Hermitian perturbations of the system. However, non-Hermitian effects, usually inaccessible in condensed-matter systems, are an important feature of photonic systems, and when added to an otherwise Hermitian Weyl material have been predicted to spread the Berry charge of the Weyl point out onto a ring of exceptional points, creating a Weyl exceptional ring and fundamentally altering its properties. Here, we observe the implications of the Weyl exceptional ring using real-space measurements of an evanescently coupled bipartite optical waveguide array by probing its effects on the Fermi arc surface states and bulk diffraction properties of the two constituent sublattices in an experimental realization of a distributed Berry charge in a topological material. The distribution of Berry charge over a ring of exceptional points, called a Weyl exceptional ring, is experimentally demonstrated.

Subfields: Atomic and Molecular Physics, and Optics, Mathematical Physics

View Paper: https://www.semanticscholar.org/paper/9220bbbdfeddb734deafb5de4c45268be1bdecad

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In Atomic and Molecular Physics, and Optics

In Mathematical Physics

Citations in the corpus

Symmetry and Topology in Non-Hermitian Physics (2018, methodology): “VII, our classification describes the non-Hermitian topological phases observed in recent experiments [145, 146, 148– 151, 153–157], which are not fitted into the previous classification scheme [122].”
Symmetry-protected nodal phases in non-Hermitian systems (2018, background): “Motivated by these insights and their recent experimental verification [36, 37], the purpose of this work is to shed light on the role of symmetry protection of EPs in NH systems, resulting in the discovery of new symmetry protected NH phases that have no immediate Hermitian analog.”
Roadmap on topological photonics (2022, background): “By realizing a Weyl exceptional ring, researchers were able to observe topological transitions in waveguide lattices [76].”
Exceptional topology of non-Hermitian systems (2019, unknown): “, without relying on fine-tuning or symmetries, form closed nodal lines in reciprocal space rather than occurring at isolated points (Cerjan et al., 2019; Xu et al., 2017).”
Higher-order non-Hermitian skin effect (2020, unknown): “[107] A.”