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Non-Hermitian systems host band degeneracies that are fundamentally distinct from those in Hermitian systems, most notably exceptional points (EPs) where both eigenvalues and eigenvectors coalesce. In three dimensional (3D) non-Hermitian…

Mesoscale and Nanoscale Physics · Physics 2026-03-12 Bin Jiang , Aolong Guo , Qilin Cai , Jian-Hua Jiang

We investigate the existence of higher order exceptional points (EPs) in non-Hermitian systems, and show that $\mu$-fold EPs are stable in $\mu-1$ dimensions in the presence of anti-unitary symmetries that are local in parameter space, such…

Mesoscale and Nanoscale Physics · Physics 2021-10-27 Pierre Delplace , Tsuneya Yoshida , Yasuhiro Hatsugai

Exceptional points (EPs) in non-Hermitian photonic systems have attracted considerable research interest due to their singular eigenvalue topology and associated anomalous physical phenomena. These properties enable diverse applications…

Optics · Physics 2025-10-17 Kaiyuan Wang , Qi Jie Wang , Matthew R. Foreman , Yu Luo

Lasing and coherent perfect absorption (CPA) are time-reversed manifestations of non-Hermitian light-matter interactions. While exceptional points (EPs) have been extensively explored for controlling lasing dynamics, their role in the…

Optics · Physics 2026-05-26 Arnab Laha , Somnath Ghosh , Adam Miranowicz , Lin Wu

Unlike a real magnetic field, which separates the energy levels of particle with opposite spin polarization, a complex field can lead to a special kind of spectral degeneracy, known as exceptional point (EP), at which two spin eigenmodes…

Mesoscale and Nanoscale Physics · Physics 2020-09-29 K. L. Zhang , Z. Song

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

One of the most fascinating and puzzling aspects of non-Hermitian systems is their spectral degeneracies, i.e., exceptional points (EPs), at which both eigenvalues and eigenvectors coalesce to form a defective state space. While coupled…

Mesoscale and Nanoscale Physics · Physics 2023-03-08 Kuangyin Deng , Xin Li , Benedetta Flebus

The exotic physics emerging in non-Hermitian systems with balanced distributions of gain and loss has drawn a great deal of attention in recent years. These systems exhibit phase transitions and exceptional point singularities in their…

Optics · Physics 2021-03-17 Arik Bergman , Robert Duggan , Kavita Sharma , Moshe Tur , Avi Zadok , Andrea Alu

The emergence of various types of degeneracies plays a crucial role in optimizing and engineering different physical phenomena in non-Hermitian physics. In our work, we focus on the derogatory Exceptional Points (EPs), which are…

Quantum Physics · Physics 2026-04-22 Grigory A. Starkov , Sharareh Sayyad

The multipartite non-Hermitian Su-Schrieffer-Heeger model is explored as a prototypical example of one-dimensional systems with several sublattice sites for unveiling intriguing insulating and metallic phases with no Hermitian counterparts.…

Mesoscale and Nanoscale Physics · Physics 2022-05-10 Ritu Nehra , Dibyendu Roy

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

As an exclusive feature of a non-Hermitian system, the existence of exceptional points (EPs) depends not only on the details of the Hamiltonian but also on the particle-number filling and the particle statistics. In this paper, we study…

Strongly Correlated Electrons · Physics 2025-09-24 J. Y. Liu-Sun , Z. Song

Exceptional bound (EB) states represent an unique new class of robust bound states protected by the defectiveness of non-Hermitian exceptional points. Conceptually distinct from the more well-known topological states and non-Hermitian skin…

Quantum Physics · Physics 2024-07-02 Deyuan Zou , Tian Chen , Haiyu Meng , Yee Sin Ang , Xiangdong Zhang , Ching Hua Lee

The complex eigenenergies and non-orthogonal eigenstates of non-Hermitian systems exhibit unique topological phenomena that cannot appear in Hermitian systems. Representative examples are the non-Hermitian skin effect and exceptional…

Quantum Physics · Physics 2025-12-19 Jung-Wan Ryu , Jae-Ho Han , Chang-Hwan Yi , Hee Chul Park , Moon Jip Park

Complex spectra of dissipative quantum systems may exhibit degeneracies known as exceptional points (EPs). At these points the systems' dynamics may undergo drastic changes. Phenomena associated with EPs and their applications have been…

Quantum Physics · Physics 2025-03-19 Andrei I. Pavlov , Yuval Gefen , Alexander Shnirman

We reveal how symmetry protected nodal points in topological semimetals may be promoted to pairs of generically stable exceptional points (EPs) by symmetry-breaking fluctuations at the onset of long-range order. This novel route to…

Strongly Correlated Electrons · Physics 2023-10-09 Lorenzo Crippa , Giorgio Sangiovanni , Jan Carl Budich

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…

The emergence of exceptional points in non-Hermitian systems represents an intriguing phenomenon characterized by the coalescence of eigenenergies and eigenstates. When a system approaches an exceptional point, it exhibits a heightened…

Mesoscale and Nanoscale Physics · Physics 2025-05-21 Shu-Xuan Wang , Zhongbo Yan

We introduce the exceptional topological insulator (ETI), a non-Hermitian topological state of matter that features exotic non-Hermitian surface states which can only exist within the three-dimensional topological bulk embedding. We show…

Mesoscale and Nanoscale Physics · Physics 2021-10-04 M. Michael Denner , Anastasiia Skurativska , Frank Schindler , Mark H. Fischer , Ronny Thomale , Tomáš Bzdušek , Titus Neupert

We study the band structure and scattering of in-plane coupled longitudinal and shear stress waves in linear layered media and observe that exceptional points (EP) appear for elastic (lossless) media, when parameterized with real-valued…

Applied Physics · Physics 2025-08-12 Vahidreza Alizadeh , Alireza V. Amirkhizi