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Unidirectional reflectionlessness is investigated in a waveguide quantum electrodynamics system that consists of a cavity and a $\Lambda$-type three-level quantum dot coupled to a one-dimensional plasmonic waveguide. Analytical expressions…

Quantum Physics · Physics 2022-07-13 De-Xiu Qiu , Fude Li , K. Xue , X. X. Yi

Exceptional points (EPs), singularities of non-Hermitian physics where complex spectral resonances degenerate, are one of the most exotic features of nonequilibrium open systems with unique properties. For instance, the emission rate of…

Recently, a local and imperfect chirality of the resonant eigenmode at the exceptional point (EP) has been reported in the optical whispering gallery microcavity system perturbed by two strong nanoscatterers [Phys. Rev. A 108, L041501…

Optics · Physics 2025-07-28 Junda Zhu , Haitao Liu , Fang Bo , Can Tao , Guoquan Zhang , Jingjun Xu

Exceptional points (EPs) represent a distinct type of spectral singularity in non-Hermitian systems, and intriguing physics concepts have been studied with optical EPs recently. As a system beyond photonics, the mechanical oscillators…

Optics · Physics 2023-02-09 Ning Wu , Kaiyu Cui , Qiancheng Xu , Xue Feng , Fang Liu , Wei Zhang , Yidong Huang

The exotic physics emerging at singularities has long attracted intense theoretical and experimental attention. In non-Hermitian systems, exceptional points (EPs), unique spectral singularities, have given rise to a host of intriguing wave…

Optics · Physics 2026-04-14 Kai Bai , Chen Lin , Jia-Zheng Li , Meng Xiao

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

Exceptional points (EPs) in open optical systems are rigorously studied using the resonant-state expansion (RSE). A spherical resonator, specifically a homogeneous dielectric sphere in a vacuum, perturbed by two point-like defects which…

Optics · Physics 2024-09-18 Kyle S. Netherwood , Hannah K. Riley , Egor A. Muljarov

Exceptional points (EPs) in non-Hermitian systems have recently attracted wide interests and spawned intriguing prospects for enhanced sensing. However, EPs have not yet been realized in thermal atomic ensembles, which is one of the most…

Quantum Physics · Physics 2023-06-30 Chao Liang , Yuanjiang Tang , An-Ning Xu , Yong-Chun Liu

Exceptional points (EPs) are degeneracy of non-Hermitian Hamiltonians, at which the eigenvalues, along with their eigenvectors, coalesce. Their orders are given by the Jordan decomposition. Here, we focus on higher-order EPs arising in…

Quantum Physics · Physics 2023-04-18 Kang Yang , Ipsita Mandal

In non-Hermitian systems, the defective band degeneracies, so-called exceptional points (EPs), can form robust exceptional lines (ELs) in 3D momentum space in the absence of any symmetries. Here, we show that a natural orientation can be…

Optics · Physics 2022-12-13 Ruo-Yang Zhang , Xiaohan Cui , Wen-Jie Chen , Zhao-Qing Zhang , C. T. Chan

A Dirac point in the Hermitian photonic system will split into a pair of exceptional points (EPs) or even spawn a ring of EPs if non-Hermiticity is involved. Here, we present a new type of non-Hermitian Dirac point which is situated in the…

Optics · Physics 2024-04-29 Jun Wang , Jie Liu , Peng Hu , Qiao Jiang , Dezhuan Han

Exceptional points (EPs) are singularities that arise in non-Hermitian physics. Current research efforts focus only on systems supporting isolated EPs characterized by increased sensitivity to external perturbations, which makes them…

Exceptional point (EP) is a spectral singularity in non-Hermitian systems. The passing over the EP leads to a phase transition, which endows the system with unconventional features that find a wide range of applications. However, the need…

Quantum Physics · Physics 2023-04-19 T. T. Sergeev , A. A. Zyablovsky , E. S. Andrianov , Yu. E. Lozovik

Exceptional points (EPs) in quasinormal mode (QNM) spectra are non-Hermitian degeneracies at which both the eigenvalues and eigenfunctions coalesce. In this paper, we identify an EP in the scalar QNM spectrum of hairy black holes in the…

General Relativity and Quantum Cosmology · Physics 2026-04-01 Lang Cheng , Xiaobo Guo , Yuhan Li , Jun Tao , Peng Wang

One of the key features of non-Hermitian systems is the occurrence of exceptional points (EPs), spectral degeneracies where the eigenvalues and eigenvectors merge. In this work, we propose applying neural networks to characterize EPs by…

Disordered Systems and Neural Networks · Physics 2023-12-05 Md. Afsar Reja , Awadhesh Narayan

Exceptional points (EPs) are non-Hermitian spectral degeneracies marking a simultaneous coalescence of eigenvalues and eigenvectors. Despite the fact that multiband $n$-fold EPs (EP$n$s) generically emerge as special points on manifolds of…

Optics · Physics 2026-03-16 Anton Montag , Jordan Isaacs , Marcus Stålhammar , Flore K. Kunst

Unconventional $p$-wave magnets (UPMs) with odd-parity spin textures have attracted interest for their zero net magnetization and anisotropic spin-split Fermi surfaces. Here, we explore a non-Hermitian open quantum system composed of a…

Mesoscale and Nanoscale Physics · Physics 2025-08-05 Mohammad Alipourzadeh , Davood Afshar , Yaser Hajati

We report a specially configured non-Hermitian optical microcavity, imposing spatially imbalanced gain-loss profile, to host an exclusively proposed next nearest neighbor resonances coupling scheme. Adopting scattering matrix (S-matrix)…

Optics · Physics 2017-10-11 Arnab Laha , Abhijit Biswas , Somnath Ghosh

Exceptional points (EPs) in non-Hermitian systems are branch singularities where eigenvalues and eigenvectors simultaneously coalesce, leading to rich topological phenomena beyond those in Hermitian systems. In this work, we systematically…

Optics · Physics 2025-09-12 Jung-Wan Ryu , Jae-Ho Han , Chang-Hwan Yi

One of the unique features of non-Hermitian~(NH) systems is the appearance of non-Hermitian degeneracies known as exceptional points~(EPs). The extensively studied defective EPs occur when the Hamiltonian becomes non-diagonalizable. Aside…

Quantum Physics · Physics 2023-12-11 Sharareh Sayyad , Marcus Stalhammar , Lukas Rodland , Flore K. Kunst