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The occurrence of exceptional points (EPs) is a fascinating non-Hermitian feature of open systems. A level-repulsion phenomenon between two complex states of an open system can be realized by positioning an EP and its time-reversal (T)…

Optics · Physics 2024-05-15 Arnab Laha , Adam Miranowicz , R. K. Varshney , Somnath Ghosh

Exceptional points (EPs), at which more than one eigenvalue and eigenvector coalesce, are unique spectral features of Non-Hermiticity (NH) systems. They exist widely in open systems with complex energy spectra. We experimentally demonstrate…

We investigate experimentally and analytically the coalescence of reflectionless (RL) states in symmetric complex wave-scattering systems. We observe RL-exceptional points (EPs), first, with a conventional Fabry-Perot system for which the…

Classical Physics · Physics 2022-06-01 Clément Ferise , Philipp del Hougne , Simon Félix , Vincent Pagneux , Matthieu Davy

The dynamical encirclement around a second order exceptional point (EP) and corresponding chirality driven nonadiabatic modal dynamics have attracted enormous attention in the topological study of various non-Hermitian systems. However,…

Optics · Physics 2020-04-08 Sibnath Dey , Arnab Laha , Somnath Ghosh

Degeneracies of non-Hermitian Hamiltonian i.e., exceptional points (EPs) of parity-time (PT)-symmetric systems have received considerable research attention due to their various possible applications in optical devices. At EPs, at least two…

Optics · Physics 2024-02-05 Priyanka Chaudhary , Akhilesh Kumar Mishra

The unique properties of exceptional point (EP) singularities, arising from non-Hermitian physics, have unlocked new possibilities for manipulating light-matter interactions. A tailored gain-loss variation, while encircling higher-order EPs…

We study quasiscarring phenomenon and mode branching at an exceptional point (EP) in typically deformed microcavities. It is shown that quasiscarred (QS) modes are dominant in some mode group and their pattern can be understood by…

Chaotic Dynamics · Physics 2015-05-27 Jung-Wan Ryu , Soo-Young Lee

Exciton-polaritons (EPs) are part-light part-matter quasiparticles that combine large exciton-mediated nonlinearities with long-range coherence, ideal for energy harvesting and nonlinear optics. Optimizing EPs for these applications is…

Optics · Physics 2025-12-05 Yongseok Hong , Ding Xu , Milan Delor

Exceptional points (EPs) are non-Hermitian singularities associated with the coalescence of individual eigenvectors accompanied by the degeneracy of their complex energies. Here, we report the discovery of a generalization to the concept of…

Quantum Physics · Physics 2026-05-07 Zhen Li , Xulong Wang , Rundong Cai , Kenji Shimomura , Congwei Lu , Zhesen Yang , Masatoshi Sato , Guancong Ma

Exceptional points~(EPs) appear as degeneracies in the spectrum of non-Hermitian matrices at which the eigenvectors coalesce. In general, an EP of order $n$ may find room to emerge if $2(n-1)$ real constraints are imposed. Our results show…

Quantum Physics · Physics 2022-07-29 Sharareh Sayyad , Flore K. Kunst

We investigate the spectral properties of a class of hard-wall bounded systems, described by potentials exhibiting domain-wise different local symmetries. Tuning the distance of the domains with locally symmetric potential from the hard…

Other Condensed Matter · Physics 2019-01-23 I. Kiorpelidis , F. K. Diakonos , G. Theocharis , V. Pagneux , O. Richoux , P. Schmelcher , P. A. Kalozoumis

Engineering the transport of radiation and its interaction with matter using non-Hermiticity, particularly through spectral degeneracies known as exceptional points(EPs), is an emerging field that has both fundamental and practical…

Optics · Physics 2022-03-03 S. Soleymani , Q. Zhong , M. Mokim , S. Rotter , R. El-Ganainy , S. K. Ozdemir

Exceptional points (EPs) promise revolutionary control over quantum light-matter interactions. Here, we experimentally demonstrate flexible and reversible engineering of quantum vacuum fluctuation in an integrated microcavity supporting…

The optical theorem relates the total scattering cross-section of a given structure with its forward scattering, but does not impose any restrictions on other directions. Strong backward-forward asymmetry in scattering could be achieved by…

Other Condensed Matter · Physics 2016-11-22 Vitali Kozlov , Dmitry Filonov , Alexander S. Shalin , Ben Z. Steinberg , Pavel Ginzburg

Dynamically encircling an exceptional point (EP) in parity-time (PT) symmetric systems shows an interesting chiral dynamics, leading to asymmetric mode switching in which the output modes are different when the encircling direction is…

Optics · Physics 2019-10-16 Xu-Lin Zhang , Tianshu Jiang , Hong-Bo Sun , C. T. Chan

Motivated by the prospect of chiral-mode control in compact photonic systems, we analyze discrete coupled single-mode resonators. Using the minimal three-resonator model, we show that an infinitesimal complex onsite perturbation near a…

Optics · Physics 2026-05-18 Kota Yagi , Takahiro Uemura , Yuto Moritake , Adam Mock , Masaya Notomi

We derive new exceptional point (EP) conditions of the coupled microring resonators using coupled mode theory in space, a more accurate approach than the commonly used coupled mode theory in time. Transmission spectra around EPs obtained…

Optics · Physics 2024-10-24 Kunpeng Zhu , Xiaoyan Zhou , Yinxin Zhang , Zhanhua Huang , Lin Zhang

Exceptional points (EPs) are remarkable spectral degeneracies in a non-Hermitian system's parameter space, where both eigenvalues and eigenstates coalesce. Here, we show that in non-Hermitian molecular chiral systems the position of EPs in…

Quantum Physics · Physics 2025-12-02 Nicola Mayer , Alexander Löhr , Nimrod Moiseyev , Misha Ivanov , Olga Smirnova

Exceptional points (EPs) are spectral singularities in non-Hermitian systems where eigenvalues and their corresponding eigenstates coalesce simultaneously. In this study, we calculate scattering poles in an open spherical solid and propose…

Classical Physics · Physics 2024-09-16 Hiroaki Deguchi , Kei Matsushima , Takayuki Yamada

Exceptional points of order $n$ (EP$n$s) appear in non-Hermitian systems as points where the eigenvalues and eigenvectors coalesce. They emerge if $2(n-1)$ real constraints are imposed, such that EP2s generically appear in two dimensions…

Mesoscale and Nanoscale Physics · Physics 2024-06-07 Anton Montag , Flore K. Kunst