Observation of bulk Fermi arc and polarization half charge from paired exceptional points

By Hengyun Zhou, Chao Peng, Y. Yoon, Chia Wei Hsu, Keith A. Nelson, Liang Fu, John D. Joannopoulos, Marin Soljačić, B. Zhen. Science, 2017

638 citations recorded by the source corpus.

Exploring photonic topology Scattering topological effects are being explored in a variety of electronic and optical materials systems owing to their robustness against defects (see the Perspective by Özdemir). Yang et al. designed and fabricated an ideal optical analog of a three-dimensional Weyl system. Angular transmission measurements revealed four Weyl points at the same energy, as well as the signature helicoidal arcs associated with such an exotic topological system. Zhou et al. theoretically proposed and experimentally demonstrated the formation of a topologically protected bulk Fermi arc. They attributed the formation of the arc to the topological nature of paired exceptional points (points at which gain and loss in the system are matched). Photonic crystals may provide a powerful platform for studying exotic properties of topological electronic systems and may also be used to develop optical devices that exploit topological properties of light-matter interactions. Science, this issue p. 1013, p. 1009; see also p. 995 Photonic crystals provide a powerful platform to study topological effects in non-Hermitian systems. The ideas of topology have found tremendous success in closed physical systems, but even richer properties exist in the more general open or dissipative framework. We theoretically propose and experimentally demonstrate a bulk Fermi arc that develops from non-Hermitian radiative losses in an open system of photonic crystal slabs. Moreover, we discover half-integer topological charges in the polarization of far-field radiation around the bulk Fermi arc. Both phenomena are shown to be direct consequences of the non-Hermitian topological properties of exceptional points, where resonances coincide in their frequencies and linewidths. Our work connects the fields of topological photonics, non-Hermitian physics, and singular optics, providing a framework to explore more complex non-Hermitian topological systems.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/7628c299a2d8bd88b8dd9dadb3c40edfddf8bc07

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In Atomic and Molecular Physics, and Optics

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Citations in the corpus

Experimental realization of a Weyl exceptional ring (2018, background): “[46] Hengyun Zhou, Chao Peng, Yoseob Yoon, Chia Wei Hsu, Keith A.”
Topological photonics (2018, background): “, 2015) as well as “Fermi arc”-type states that connect between exceptional points in two-dimensional systems (Kozii and Fu, 2017; Malzard and Schomerus, 2018a; Zhou et al., 2018); a related phenomenon was examined in the context of heavy-fermion systems (Yoshida, Peters, and Kawakami, 2018).”
A review on non-Hermitian skin effect (2022, background): “As discussed in the introduction section, the EPs refer to the singularities in non-Hermitian systems, appearing either in the parameter space [9] or the momentum space [15].”
Symmetry-protected nodal phases in non-Hermitian systems (2018, background): “Very recently, intense theoretical [7–37] and experimental [38–45] efforts have been made to extend the concept of topological band structures to non-Hermitian (NH) systems which play an important role in the effective description of dissipation effects in various physi-”
Symmetry and Topology in Non-Hermitian Physics (2018, neutral): “[152] H.”
Roadmap on topological photonics (2022, methodology): “The half charges accompanied with the EPs (figure 17(b)) are likely not topologically trivial because they reflect the non-trivial Berry phase enclosing the EPs (figure 17(a)) [149].”