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Non-Hermitian chiral degeneracy of gated graphene metasurfaces

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Abstract
Non-Hermitian degeneracies, also known as exceptional points (EPs), have been the focus of much attention due to their singular eigenvalue surface structure. Nevertheless, as pertaining to a non-Hermitian metasurface platform, the reduction of an eigenspace dimensionality at the EP has been investigated mostly in a passive repetitive manner. Here, we propose an electrical and spectral way of resolving chiral EPs and clarifying the consequences of chiral mode collapsing of a non-Hermitian gated graphene metasurface. More specifically, the measured non-Hermitian Jones matrix in parameter space enables the quantification of nonorthogonality of polarisation eigenstates and half-integer topological charges associated with a chiral EP. Interestingly, the output polarisation state can be made orthogonal to the coalesced polarisation eigenstate of the metasurface, revealing the missing dimension at the chiral EP. In addition, the maximal nonorthogonality at the chiral EP leads to a blocking of one of the cross-polarised transmission pathways and, consequently, the observation of enhanced asymmetric polarisation conversion. We anticipate that electrically controllable non-Hermitian metasurface platforms can serve as an interesting framework for the investigation of rich non-Hermitian polarisation dynamics around chiral EPs.
Issued Date
2023
Soojeong Baek
Sang Hyun Park
Donghak Oh
Kanghee Lee
Sangha Lee
Hosub Lim
Taewoo Ha
Hyun Sung Park
Shuang Zhang
Lan Yang
Bumki Min
Teun-Teun Kim
Type
Article
Keyword
MetasurfacesNon-HermitianChiral degeneracyGraphene metasurfaces
DOI
10.1038/s41377-023-01121-6
URI
https://oak.ulsan.ac.kr/handle/2021.oak/17612
Publisher
Light-Science & Applications
Language
영어
ISSN
2047-7538
Citation Volume
12
Citation Number
1
Citation Start Page
1
Citation End Page
10
Appears in Collections:
Natural Science > Physics
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