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Non-hermitian quantum systems can exhibit spectral degeneracies known as exceptional points, where two or more eigenvectors coalesce, leading to a non-diagonalizable Jordan block. It is known that symmetries can enhance the abundance of…

Quantum Physics · Physics 2022-11-15 Robin Schäfer , Jan C. Budich , David J. Luitz

Systems exhibiting degeneracies known as exceptional points have remarkable properties with powerful applications, particularly in sensor design. These degeneracies are formed when eigenstates coincide, and the remarkable effects are…

Analysis of PDEs · Mathematics 2020-08-04 Habib Ammari , Bryn Davies , Erik Orvehed Hiltunen , Hyundae Lee , Sanghyeon Yu

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

Many novel properties of non-Hermitian systems are found at or near the exceptional points-branch points of complex energy surfaces at which eigenvalues and eigenvectors coalesce. In particular, higher-order exceptional points can result in…

Optics · Physics 2019-02-21 Shubo Wang , Bo Hou , Weixin Lu , Yuntian Chen , Z. Q. Zhang , C. T. Chan

Defective spectral degeneracy, known as exceptional point (EP), lies at the heart of various intriguing phenomena in optics, acoustics, and other nonconservative systems. Despite extensive studies in the past two decades, the…

Mesoscale and Nanoscale Physics · Physics 2023-04-13 Cui-Xian Guo , Shu Chen , Kun Ding , Haiping Hu

Exceptional points (EPs) are non-Hermitian degeneracies where eigenvalues and eigenvectors coalesce, giving rise to unusual physical effects across scientific disciplines. The concept of EPs has recently been extended to nonlinear physical…

Exceptional points (EPs) are special singularities of non-Hermitian Hamiltonians. At an EP, two or more eigenvalues and the corresponding eigenstates coalesce. Recently, EP-based optical gyroscope near an EP was extensively investigated to…

Exceptional points (EPs) are spectral degeneracies unique to non-Hermitian systems which underpin phenomena from enhanced sensing to unconventional topology. While disorder is usually viewed as detrimental, it can also drive topological…

Disordered Systems and Neural Networks · Physics 2026-01-28 Xiaoyu Cheng , Tiantao Qu , Yaqing Yang , Jun Chen , Lei Zhang

Exceptional points (EPs) with their intriguing spectral topology have attracted considerable attention in a broad range of physical systems, with potential sensing applications driving much of the present research in this field. Here we…

Optics · Physics 2026-01-29 Jan Wingenbach , Stefan Schumacher , Xuekai Ma

Exceptional points, also known as non-Hermitian degeneracies, have been observed in parity-time symmetric metasurfaces as the parity-time symmetry breaking point. However, the parity-time symmetry condition puts constraints on the…

Mesoscale and Nanoscale Physics · Physics 2020-12-08 Sang Hyun Park , Sung-Gyu Lee , Taewoo Ha , Sanghyup Lee , Soo-Jeong Baek , Bumki Min , Shuang Zhang , Mark Lawrence , Teun-Teun Kim

Understanding the linear response of any system is the first step towards analyzing its linear and nonlinear dynamics, stability properties, as well as its behavior in the presence of noise. In non-Hermitian Hamiltonian systems, calculating…

Exceptional points, a remarkable phenomenon in physical systems, have been exploited for sensing applications. It has been demonstrated recently that it can also utilize as sensory threshold in which the interplay between exceptional-point…

Applied Physics · Physics 2024-10-18 Shirin Panahi , Li-Li Ye , Ying-Cheng Lai

Exceptional points featuring enhanced energy response to perturbation hold significant potential in detection and measurement of weak signals. Of particular interest is the existence and property of high-order exceptional points in quantum…

Quantum Physics · Physics 2025-03-10 Tingting Shi , Vasilii Smirnov , Kaiye Shi , Wei Zhang

We investigate non-Hermitian degeneracies, also known as exceptional points, in continous elastic media, and their potential application to the detection of mass and stiffness perturbations. Degenerate states are induced by enforcing…

Applied Physics · Physics 2021-02-24 M. I. N. Rosa , M. Mazzotti , M. Ruzzene

Non-conservative physical systems admit a special kind of spectral degeneracy, known as exceptional point (EP), at which eigenvalues and eigenvectors of the corresponding non-Hermitian Hamiltonian coalesce. Dynamical parametric encircling…

Mesoscale and Nanoscale Physics · Physics 2019-10-21 Alexey Galda , Valerii M. Vinokur

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…

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

We analyze the behavior of a non-Hermitian opened one-dimensional quantum system with $\mathcal{PT}$ symmetry. This system is built by a dimer, with balanced gains and losses described by a parameter $\gamma$. By varying $\gamma$ the system…

Quantum Physics · Physics 2024-04-11 J. Colín-Gálvez , E. Castaño , G. Báez , V. Domínguez-Rocha

Exceptional points are the branch-point singularities of non-Hermitian Hamiltonians, and have rich consequences in open-system dynamics. While the exceptional points and their critical phenomena are widely studied in the non-Hermitian…

Quantum Physics · Physics 2024-08-22 Konghao Sun , Wei Yi

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…