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We demonstrate the existence of exceptional points of degeneracy (EPD) of periodic eigenstates in non-Hermitian coupled chains of dipolar scatterers. Guided modes supported by these structures can exhibit an EPD in their dispersion diagram…

Optics · Physics 2017-03-22 Mohamed A. K. Othman , Vincenzo Galdi , Filippo Capolino

Sensors play a crucial role in advanced apparatuses and it is persistently pursued to improve their sensitivities. Recently, the singularity of a non-Hermitian system, known as the exceptional point (EP), has drawn much attention for this…

Quantum Physics · Physics 2024-01-04 Yao-Dong Hu , Yi-Pu Wang , Rui-Chang Shen , Zi-Qi Wang , Wei-Jiang Wu , J. Q. You

Higher-order exceptional points (EPs) in optical structures enable ultra-sensitive responses to perturbations. However, previous investigations on higher-order EPs have predominantly focused on coupled systems, leaving their fundamental…

Non-Hermitian systems distinguish themselves from Hermitian systems by exhibiting a phase transition point called an exceptional point (EP), which is the point at which two eigenstates coalesce under a system parameter variation. Many…

Mesoscale and Nanoscale Physics · Physics 2016-04-20 Kun Ding , Guancong Ma , Meng Xiao , Z. Q. Zhang , C. T. Chan

The non-analyticity induced by exceptional points (EPs) has manifestations not only in non-Hermitian but also in Hermitian systems. In this work, we focus on a minimal Hermitian bosonic Kitaev model to reveal the dynamical demonstration of…

Quantum Physics · Physics 2025-12-02 D. K. He , Z. Song

Controlling gain and loss of coupled optical cavities can induce non-Hermitian degeneracies of eigenstates, called exceptional points (EPs). Various unconventional phenomena around EPs have been reported, and expected to incorporate extra…

Exceptional points (EPs) are degeneracies of non-Hermitian systems, where both eigenvalues and eigenvectors coalesce. Classical and quantum systems exhibiting high-order EPs have recently been identified as fundamental building blocks for…

Exceptional points (EPs), a unique feature of non-Hermitian systems, represent degeneracies in non-Hermitian operators that likely do not occur in Hermitian systems. Nevertheless, unlike its fermionic counterpart, a Hermitian bosonic Kitaev…

Quantum Physics · Physics 2025-10-07 D. K. He , Z. Song

Exceptional points (EPs) are complex singularities of parametric linear operators where two or more eigenvalues and eigenvectors coalesce. EPs are attracting increasing interest in mechanical metamaterials due to their strong potentials for…

Applied Physics · Physics 2022-04-05 Weidi Wang , Alireza V. Amirkhizi

Exceptional points (EPs) of non-Hermitian (NH) systems have recently attracted increasing attention due to their rich phenomenology and intriguing applications. Compared to the predominantly studied second-order EPs, higher-order EPs have…

Mesoscale and Nanoscale Physics · Physics 2023-09-07 Kunkun Wang , Lei Xiao , Haiqing Lin , Wei Yi , Emil J. Bergholtz , Peng Xue

Eigenmode coalescence imparts remarkable properties to non-hermitian time evolution, culminating in a purely non-hermitian spectral degeneracy known as an exceptional point (EP). Here, we revisit time evolution at the EP and classify…

Quantum Physics · Physics 2021-11-10 Aleksi Bossart , Romain Fleury

Exceptional points are interesting physical phenomena in non-Hermitian physics at which the eigenvalues are degenerate and the eigenvectors coalesce. In this paper, we find that the universal feature of arbitrary non-Hermitian two level…

Quantum Physics · Physics 2022-01-25 X. R. Wang , F. Yang , X. J. Yu , X. Q. Tong , S. P. Kou

Exceptional points (EPs) are peculiar band singularities and play a vital role in a rich array of unusual optical phenomena and non-Hermitian band theory. In this paper, we provide a topological classification of isolated EPs based on…

Mesoscale and Nanoscale Physics · Physics 2022-06-29 Haiping Hu , Shikang Sun , Shu Chen

Exceptional points (EPs) are singularities in the spectra of non-Hermitian operators, where eigenvalues and eigenvectors coalesce. Recently, open quantum systems have been increasingly explored as EP testbeds due to their natural…

Quantum Physics · Physics 2025-02-18 Jhen-Dong Lin , Po-Chen Kuo , Neill Lambert , Adam Miranowicz , Franco Nori , Yueh-Nan Chen

Exceptional points are spectral degeneracies of non-Hermitian systems where eigenvalues and eigenvectors coalesce, inducing unique topological phases that have no counterpart in the Hermitian realm. Here we consider a non-Hermitian system…

Mesoscale and Nanoscale Physics · Physics 2023-04-10 Jorge Cayao

In our prior studies we synthesized special circuits possessing evolution matrices that involve nontrivial Jordan blocks and the corresponding degenerate eigenfrequencies. The degeneracy of this type is sometimes referred to as exceptional…

Classical Physics · Physics 2021-05-05 Alexander Figotin

Exceptional degeneracies, at which both eigenvalues and eigenvectors coalesce, and parity-time ($\mathcal{PT}$) symmetry, reflecting balanced gain and loss in photonic systems, are paramount concepts in non-Hermitian systems. We here…

Mesoscale and Nanoscale Physics · Physics 2021-11-16 Marcus Stålhammar , Emil J. Bergholtz

A special kind of degeneracies known as the exceptional points (EPs), for resonant states on a dielectric periodic slab, are investigated. Due to their unique properties, EPs have found important applications in lasing, sensing,…

Optics · Physics 2018-06-20 Amgad Abdrabou , Ya Yan Lu

We present the experimental demonstration of the occurrence of exceptional points of degeneracy (EPDs) in a single resonator by introducing a linear time-periodic variation of one of its components, in contrast to EPDs in parity time…

Exceptional point (EP) is exclusive for non-Hermitian system and distinct from that at a degeneracy point (DP), supporting intriguing dynamics, which can be utilized to probe quantum phase transition and prepare eigenstates in a Hermitian…

Quantum Physics · Physics 2021-12-10 P. Wang , K. L. Zhang , Z. Song