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Exceptional point and spectral singularity are two types of singularity that are unique to non-Hermitian systems. Here, we report the high-order spectral singularity as a high-order pole of the scattering matrix for a non-Hermitian…

Optics · Physics 2023-06-12 H. S. Xu , L. C. Xie , L. Jin

Exceptional points, that are spectral degeneracies in the parameter space of non-Hermitian systems, have evoked a massive interest in the optical domain owing to their striking consequences on optical behavior of commonly known systems.…

Optics · Physics 2023-01-18 Krishna Joshi , Sushil Mujumdar

The nontrivial degeneracies in non-Hermitian systems, exceptional points (EPs), have attracted extensive attention due to intriguing phenomena. Compared with commonly observed second-order EPs, high-order EPs show rich physics due to their…

Quantum Physics · Physics 2024-12-16 Yue Li , Yang Wu , Yuqi Zhou , Mengxiang Zhang , Xingyu Zhao , Yibo Yuan , Xu Cheng , Yi Li , Xi Qin , Xing Rong , Yiheng Lin , Jiangfeng Du

Non-Hermiticity naturally breaks down the adiabaticity and thus leads to non-Abelian behaviors in multi-band systems. Here, we study how non-Abelian properties emerge in non-Hermitian systems by considering a multi-band non-Hermitian model…

Mesoscale and Nanoscale Physics · Physics 2025-09-17 Ziyu Zhou , Zhi-Cong Xu , Li-Jun Lang

We systematically investigate the finite-size effects in non-Hermitian one-dimensional (1D) Su-Schrieffer-Heeger (SSH) and two-dimensional (2D) Chern insulator models. Using a combination of analytical and numerical calculations, we show…

Mesoscale and Nanoscale Physics · Physics 2019-04-30 Rui Chen , Chui-Zhen Chen , Bin Zhou , Dong-Hui Xu

One of the most surprising features of effectively non-Hermitian physical systems is their potential to exhibit a striking nonlinear response and fragility to small perturbations. This feature arises from spectral singularities known as…

Mesoscale and Nanoscale Physics · Physics 2026-02-05 Subhajyoti Bid , Henning Schomerus

The union of topology and non-Hermiticity has led to the unveiling of many intriguing phenomena. We introduce a synthetic spin-engineered model belonging to symmetry class AI, which is a rare occurrence, and demonstrate the emergence of a…

Mesoscale and Nanoscale Physics · Physics 2024-05-08 Ronika Sarkar , Ayan Banerjee , Awadhesh Narayan

In this work we study many-body 'steady states' that arise in the non-Hermitian generalisation of the non-interacting Su-Schrieffer-Heeger model at a finite density of fermions. We find that the hitherto known phase diagrams for this…

Mesoscale and Nanoscale Physics · Physics 2022-05-17 Ayan Banerjee , Suraj S. Hegde , Adhip Agarwala , Awadhesh Narayan

The current understanding of the role of topology in non-Hermitian (NH) systems and its far-reaching physical consequences observable in a range of dissipative settings are reviewed. In particular, how the paramount and genuinely NH concept…

Mesoscale and Nanoscale Physics · Physics 2021-03-03 Emil J. Bergholtz , Jan Carl Budich , Flore K. Kunst

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

Exceptional points (EPs) are singularities in the parameter space of a non-Hermitian system where eigenenergies and eigenstates coincide. They hold promise for enhancing sensing applications, but this is limited by the divergence of shot…

Optics · Physics 2025-04-07 Xu Zheng , Y. D. Chong

Non-Hermitian systems with parity-time ($\mathcal{PT}$) symmetry and anti-$\mathcal{PT}$ symmetry give rise to exceptional points (EPs) with intriguing properties related to, e.g., chiral transport and enhanced sensitivity, due to the…

Quantum Physics · Physics 2022-04-19 Hossein Rangani Jahromi , Rosario Lo Franco

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 facilitate peculiar dynamics in non-Hermitian systems. Yet, in photonics, they have mainly been studied in the classical realm. In this work, we reveal the behavior of two-photon quantum states in non-Hermitian systems…

Exceptional points are complex-valued spectral singularities that lead to a host of intriguing features such as loss-induced transparency - a counterintuitive process in which an increase in the system's overall loss can lead to enhanced…

Quantum Physics · Physics 2021-12-13 Konrad Tschernig , Kurt Busch , Demetrios N. Christodoulides , Armando Perez-Leija

Several works have recently addressed the emergence of exceptional points (EPs), i.e., spectral singularities of non-Hermitian Hamiltonians, in the long-wavelength dynamics of coupled magnetic systems. Here, by focusing on the driven…

Mesoscale and Nanoscale Physics · Physics 2023-01-04 Xin Li , Kuangyin Deng , Benedetta Flebus

We propose and systematically analyze a practical scheme for implementing a one-dimensional non-Hermitian Su-Schrieffer-Heeger model using individually addressable Rydberg atom arrays. Our setup consists of an atomic chain with three-atom…

Quantum Physics · Physics 2026-01-29 J. N. Bai , F. Yang , D. Yan , Weibin Li , X. Q. Shao

This paper experimentally investigates topologically protected edge modes in a water wave channel through a direct geometric mapping to the one-dimensional Su-Schrieffer-Heeger (SSH) model. By designing a periodic channel with alternating…

The three-disk scatterer has served as a paradigm for semiclassical periodic orbit quantization of classical chaotic systems using Gutzwiller's trace formula. It represents an open quantum system, thus leading to spectra of complex…

Chaotic Dynamics · Physics 2017-07-14 Niklas Liebermann , Jörg Main , Günter Wunner

Exceptional points (EPs) are special spectral degeneracies of non-Hermitian Hamiltonians governing the dynamics of open systems. At the EP two or more eigenvalues and the corresponding eigenstates coalesce. Recently, it has been proposed…

Optics · Physics 2020-02-19 Yu-Hung Lai , Yu-Kun Lu , Myoung-Gyun Suh , Kerry Vahala