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Dirac points (DP) in Hermitian systems play a key role in topological phenomena. Their existence in non-Hermitian systems is then desirable, but the addition of loss or gain transforms DPs into pairs of Exceptional Points (EPs) joined by a…

Optics · Physics 2024-04-10 Pilar Pujol-Closa , Lluis Torner , David Artigas

Recently, there has been a lot of activity in the research field of topological non-Hermitian physics, partly driven by fundamental interests and partly driven by applications in photonics. However, despite these activities, a general…

Mesoscale and Nanoscale Physics · Physics 2019-06-26 W. B. Rui , Y. X. Zhao , Andreas P. Schnyder

We present the observation of diabolic points in Hermitian and non-Hermitian electronics dimers. The condition of unbreakable Parity-time symmetry is established for both PT-symmetric ZRC and RLC dimers. We show how appears non-Hermitian…

Applied Physics · Physics 2020-05-25 Stéphane Boris Tabeu , Fernande Fotsa-Ngaffo , Aurélien Kenfack-Jiotsa

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

We propose an efficient optomechanical mass sensor operating at exceptional points (EPs), non-hermitian degeneracies where eigenvalues of a system and their corresponding eigenvectors simultaneously coalesce. The benchmark system consists…

Mesoscale and Nanoscale Physics · Physics 2019-08-07 P. Djorwé , Y. Pennec , B. Djafari-Rouhani

Eigenstate coalescence in non-Hermitian systems is widely observed in diverse scientific domains encompassing optics and open quantum systems. Recent investigations have revealed that adiabatic encircling of exceptional points (EPs) leads…

Quantum Physics · Physics 2023-06-13 Jung-Wan Ryu , Jae-Ho Han , Chang-Hwan Yi , Moon Jip Park , Hee Chul Park

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

The study of non-Hermitian degeneracies -- called exceptional points -- has become an exciting frontier at the crossroads of optics, photonics, acoustics, and quantum physics. Here, we introduce the Newton polygon method as a general…

Mesoscale and Nanoscale Physics · Physics 2023-08-22 Rimika Jaiswal , Ayan Banerjee , Awadhesh Narayan

Exceptional points (EPs) are truly non-Hermitian (NH) degeneracies where matrices become defective. The order of such an EP is given by the number of coalescing eigenvectors. On the one hand, most work focuses on studying $N$th-order EPs in…

Mesoscale and Nanoscale Physics · Physics 2024-11-11 Julius T. Gohsrich , Jacob Fauman , Flore K. Kunst

Hyperbolic lattices are starting to be explored in search of novel phases of matter. At the same time, non-Hermitian physics has come to the forefront in photonic, optical, phononic, and condensed matter systems. In this work, we introduce…

Mesoscale and Nanoscale Physics · Physics 2024-04-30 Nisarg Chadha , Awadhesh Narayan

The concept of exceptional point (EP) is demonstrated experimentally in the case of a simple mechanical system consisting of two linearized coupled pendulums. Exceptional points correspond to specific values of the system parameters that…

Computational Physics · Physics 2024-02-08 Nicolas Even , Benoit Nennig , Gautier Lefebvre , Emmanuel Perrey-Debain

Compared with Hermitian theory, non-Hermitian physics offers a fundamentally different mathematical framework, enabling the observation of topological phenomena that have no analogue in Hermitian systems. Among these, the exceptional point…

Quantum Physics · Physics 2025-09-24 Zhong-Sheng Chen , Wei-Xin Chen , Fan Wu , Zhong-Wei Xu , Jing Ma , Yun-Kun Jiang , Huai-Zhi Wu , Shi-Biao Zheng

Higher-order exceptional points (EPs) in non-Hermitian systems have attracted great interest due to their advantages in sensitive enhancement and distinct topological features. However, realization of such EPs is still challenged because…

Quantum Physics · Physics 2022-09-29 Wei Xiong , Zhuanxia Li , Guo-Qiang Zhang , Mingfeng Wang , Hai-Chao Li , Xiao-Qing Luo , Jianjiao Chen

Exceptional points (EPs) are singular points on a parameter space at which some eigenvalues (scattering poles) and their corresponding eigenmodes coalesce. This study shows the existence of second- and third-order EPs in cylindrical elastic…

Classical Physics · Physics 2023-04-26 Kei Matsushima , Yuki Noguchi , Takayuki Yamada

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 optics has revealed a series of counterintuitive phenomena with profound implications for sensing, lasing, and light manipulation. While the non-Hermiticity of Hamitonians is well-recognized, recent advancements in…

Optics · Physics 2024-04-19 Jipeng Xu , Yuanhao Mao , Jianfa Zhang , Biao Yang , Ken Liu , Zhihong Zhu

In this article we study 3D non-Hermitian higher-order Dirac semimetals (NHHODSMs). Our focus is on $C_4$-symmetric non-Hermitian systems where we investigate inversion ($\mathcal{I}$) or time-reversal ($\mathcal{T}$) symmetric models of…

Mesoscale and Nanoscale Physics · Physics 2021-11-10 Sayed Ali Akbar Ghorashi , Tianhe Li , Masatoshi Sato , Taylor L. Hughes

We have investigated the exceptional points (EPs) which are degeneracies of a non-Hermitian Hamiltonian, in the case that three modes are interacting with each other. Even though the parametric evolution of the modes cannot be uniquely…

Quantum Physics · Physics 2015-05-30 Jung-Wan Ryu , Soo-Young Lee , Sang Wook Kim

We theoretically study diverse exceptional points (EPs) in an experimentally feasible magno-optomechanics consisting of an optomechanical subsystem coupled to a magnomechanical subsystem via physically direct contact. By adiabatically…

Quantum Physics · Physics 2024-11-14 Wen-Di He , Xiao-Hong Fan , Ming-Yue Liu , Guo-Qiang Zhang , Hai-Chao Li , Wei Xiong

Lines of exceptional points are robust in the 3-dimensional non-Hermitian parameter space without requiring any symmetry. However, when more elaborate exceptional structures are considered, the role of symmetry becomes critical. One such…

Quantum Physics · Physics 2023-12-18 Xiaohan Cui , Ruo-Yang Zhang , Xulong Wang , Wei Wang , Guancong Ma , C. T. Chan