Journal
FRONTIERS IN PHYSICS
Volume 10, Issue -, Pages -Publisher
FRONTIERS MEDIA SA
DOI: 10.3389/fphy.2022.845624
Keywords
zero refractive index; photonic; phononic band structure; metamaterials; Dirac; Dirac-like cones; non-Hermitian optics
Categories
Funding
- National Key R&D Program of China [2020YFA0211300, 2020YFA0211400, 2017YFA0303702]
- National Natural Science Foundation of China [11974176, 12174188]
- China Postdoctoral Science Foundation [2021M702401]
- Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
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Accidental degeneracy plays a vital role in the generation of novel band dispersions. Structures exhibiting accidental Dirac-like conical dispersion at the center of the Brillouin zone can have unique features, such as zero-index behavior and wave tunneling. Introduction of non-Hermiticity in the system can lead to appearance of exceptional points and various other unique dispersions. Similar phenomena are observed in phononic structures.
Accidental degeneracy plays an important role in the generation of novel band dispersions. Photonic structures that exhibit an accidental Dirac-like conical dispersion at the center of the Brillouin zone can behave like a zero-index material at the Dirac-point frequency, leading to a number of unique features, such as invariant phase in space, wave tunneling, photonic doping and anti-doping, etc. Such a phenomenon has been explored in on-chip structures or three dimensions recently. The introduction of non-Hermiticity into the system via loss or gain could transform the accidental Dirac-like cone into a spawning ring of exceptional points, a complex Dirac-like cone or other unique dispersions. Similar Dirac-like cones and related physics are also observed in phononic structures. This review presents an overview of the accidental-degeneracy-induced Dirac-like cones at the center of the Brillouin zone in both photonic and phononic structures, including the fundamental physics, effective-medium description and experimental demonstration, as well as current challenges and future directions.
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