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Emergence of exceptional points in two dimensions is one of the remarkable phenomena in non-Hermitian systems. We here elucidate the impacts of symmetry on the non-Hermitian physics. Specifically, we analyze chiral symmetric correlated…

Strongly Correlated Electrons · Physics 2019-03-13 Tsuneya Yoshida , Robert Peters , Norio Kawakami , Yasuhiro Hatsugai

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

Spontaneous symmetry breaking (SSB) and exceptional points (EPs) are often assumed to be inherently linked. Here we investigate the intricate relationship between SSB and specific classes of EPs across three distinct, real-world scenarios…

We characterise non-Hermitian Fabry-P\'erot resonances in high-contrast resonator systems and study the properties of their associated resonant modes from continuous differential models. We consider two non-Hermitian effects: the…

Mathematical Physics · Physics 2026-02-13 Habib Ammari , Erik Orvehed Hiltunen , Bowen Li , Ping Liu , Jiayu Qiu , Yingjie Shao , Alexander Uhlmann

Exceptional points play a pivotal role in the topology of non-Hermitian systems, and significant advances have been made in classifying exceptional points and exploring the associated phenomena. Exceptional surfaces, which are hypersurfaces…

Materials Science · Physics 2022-09-08 Hongwei Jia , Ruo-Yang Zhang , Jing Hu , Yixin Xiao , Yifei Zhu , C. T. Chan

Non-Hermitian spectral degeneracies, known as exceptional points (EPs), feature simultaneous coalescence of both eigenvalues and the associated eigenstates of a system. A host of intriguing EP effects and their applications have been…

Quantum Physics · Physics 2022-05-24 R. Huang , Ş. K. Özdemir , J. -Q. Liao , F. Minganti , L. -M. Kuang , Franco Nori , H. Jing

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

Non-Hermitian systems distinguish themselves from Hermitian systems by exhibiting a phase transition point called an exceptional point (EP), which is the point at which two eigenstates coalesce under a system parameter variation. Many…

Mesoscale and Nanoscale Physics · Physics 2016-04-20 Kun Ding , Guancong Ma , Meng Xiao , Z. Q. Zhang , C. T. Chan

We analyze a two-dimensional Kondo lattice model with special emphasis on non-Hermitian properties of the single-particle spectrum, following a recent proposal by Kozii and Fu. Our analysis based on the dynamical mean-field theory…

Strongly Correlated Electrons · Physics 2018-08-01 Tsuneya Yoshida , Robert Peters , Norio Kawakami

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…

Bound states in the continuum (BICs) and exceptional points (EPs), as two distinct physical singularities represented by complex frequencies in non-Hermitian systems, have garnered significant attention and clear definitions in their…

Non-Abelian gauge fields are versatile tools for synthesizing topological phenomena but have so far been mostly studied in Hermitian systems, where gauge flux has to be defined from a closed loop in order for gauge fields, whether Abelian…

Optics · Physics 2024-01-31 Zehai Pang , Jinbing Hu , Yi Yang

We propose and show that application of light leads to an intriguing platform for controlling exceptional points in non-Hermitian topological systems. We demonstrate our proposal using three different non-Hermitian systems -- nodal line…

Mesoscale and Nanoscale Physics · Physics 2020-12-02 Ayan Banerjee , Awadhesh Narayan

Non-Hermitian systems have attracted significant interest because of their intriguing and useful properties, including exceptional points (EPs), where eigenvalues and the corresponding eigenstates of non-Hermitian operators become…

Quantum Physics · Physics 2025-03-28 Hamed Ghaemi-Dizicheh , Shahram Dehdashti , Andreas Hanke , Ahmed Touhami , Janis Nötzel

The non-Hermiticity of the system gives rise to distinct knot topology that has no Hermitian counterpart. Here, we report a comprehensive study of the knot topology in gapped non-Hermitian systems based on the universal dilation method with…

Quantum Physics · Physics 2023-11-14 Yang Wu , Yunhan Wang , Xiangyu Ye , Wenquan Liu , Chang-Kui Duan , Ya Wang , Xing Rong , Jiangfeng Du

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

Exceptional points are spectral degeneracies of non-Hermitian systems where eigenvalues and eigenvectors coalesce, inducing unique topological phases that have no counterpart in the Hermitian realm. Here we consider a non-Hermitian system…

Mesoscale and Nanoscale Physics · Physics 2023-04-10 Jorge Cayao

Non-Hermitian band topology can give rise to phenomena with no counterparts in Hermitian systems. A well-known example is the non-Hermitian skin effect (NHSE), where Bloch eigenstates localize at a boundary, induced by a nontrivial spectrum…

Mesoscale and Nanoscale Physics · Physics 2025-08-28 Hong-Yu Zou , Bing-Bing Wang , Yong Ge , Ke-Qi Zhao , Yu-Qi Chen , Hong-Xiang Sun , Shou-Qi Yuan , Haoran Xue , Baile Zhang

We demonstrate the occurrence of nodal non-Hermitian (NH) phases featuring exceptional degeneracies in chiral-symmetric disordered quantum wires, where NH physics naturally arises from the self-energy in a disorder-averaged Green's function…

Mesoscale and Nanoscale Physics · Physics 2021-07-14 Benjamin Michen , Tommaso Micallo , Jan Carl Budich

Exceptional points (EPs) have recently attracted considerable attention in the study of non-Hermitian systems and in applications such as sensors and mode switching. In particular, nontrivial topological structures of EPs have been studied…

Quantum Physics · Physics 2022-08-17 Kyu-Won Park , Jinuk Kim , Kabgyun Jeong