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Intrinsic defects in optomechanical devices are generally viewed to be detrimental for achieving coherent amplification of phonons, and great care has thus been exercised in fabricating devices and materials with no (or a minimal number of)…

Quantum Physics · Physics 2017-11-07 H. Lü , S. K. Özdemir , Franco Nori , L. -M. Kuang , H. Jing

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

A numerical algorithm is proposed to explore in a systematic way the trajectories of the eigenvalues of non-Hermitian matrices in the parametric space and exploit this in order to find the locations of defective eigenvalues in the complex…

Computational Physics · Physics 2020-04-08 Benoit Nennig , Emmanuel Perrey-Debain

Usually, when investigating exceptional points (EPs) of an open Markovian bosonic system, one deals with spectral degeneracies of a non-Hermitian Hamiltonian (NHH), which can correctly describe the system dynamics only in the semiclassical…

Quantum Physics · Physics 2020-09-15 Ievgen I. Arkhipov , Adam Miranowicz , Fabrizio Minganti , Franco Nori

Exceptional points (EPs) are special points in non-Hermitian systems where both eigenvalues and eigenvectors coalesce. In open quantum systems, these points are typically analyzed using effective non-Hermitian Hamiltonians or Liouvillian…

Quantum Physics · Physics 2025-07-23 Wai Chun Wong , Bei Zeng , Jensen Li

Bound states in the continuum (BICs) and exceptional points (EPs) are unique singularities of non-Hermitian systems. BICs demonstrate enhancement of the electromagnetic field at the nanoscale, while EPs exhibit high sensitivity to small…

Higher-order exceptional points (EPs), resulting from non-Hermitian degeneracies, have shown greater advantages in sensitive enhancement than second-order EPs (EP2s). Therefore, seeking higher-order EPs in various quantum systems is…

Quantum Physics · Physics 2021-12-15 Wei Xiong , Zhuanxia Li , Yiling Song , Jiaojiao Chen , Guoqiang Zhang , Mingfeng Wang

Exceptional points, resulting from non-Hermitian degeneracies, have the potential to enhance the capabilities of quantum sensing. Thus, finding exceptional points in different quantum systems is vital for developing such future sensing…

Mesoscale and Nanoscale Physics · Physics 2020-01-22 Po-Chen Kuo , Neill Lambert , Adam Miranowicz , Hong-Bin Chen , Guang-Yin Chen , Yueh-Nan Chen , Franco Nori

In a laser system non-Hermitian methods such as Parity-Time (PT) Symmetry and Supersymmetry (SUSY) have shown and demonstrated the ability to suppress unwanted lasing modes and, thus, achieved single mode lasing operation through the…

The exceptional points (EPs) aroused from the non-Hermiticity bring rich phenomena, such as exceptional nodal topologies, unidirectional invisibility, single-mode lasing, sensitivity enhancement and energy harvesting. Isolated high-order…

Quantum Physics · Physics 2024-01-19 Yang Wu , Yunhan Wang , Xiangyu Ye , Wenquan Liu , Zhibo Niu , Chang-Kui Duan , Ya Wang , Xing Rong , Jiangfeng Du

Non-Hermitian systems at the exceptional point (EP) degeneracy are demonstrated to be highly sensitive to environmental perturbation. Here, we propose and theoretically investigate a novel multilayered heterostructure favoring double EPs…

Optics · Physics 2019-03-21 Jieun Yim , Han Zhao , Bikashkali Midya , Liang Feng

Unconventional $p$-wave magnets (UPMs) with odd-parity spin textures have attracted interest for their zero net magnetization and anisotropic spin-split Fermi surfaces. Here, we explore a non-Hermitian open quantum system composed of a…

Mesoscale and Nanoscale Physics · Physics 2025-08-05 Mohammad Alipourzadeh , Davood Afshar , Yaser Hajati

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

The fascinating realm of non-Hermitian physics with the interplay of parity (P) and time-reversal (T) symmetry has been witnessing immense attention in exploring unconventional physics at Exceptional Point (EP) singularities. Particularly,…

Optics · Physics 2024-05-20 Dinesh Beniwal , Arnab Laha , Adam Miranowicz , Somnath Ghosh

The physics of exceptional point (EP) singularities, has been a key to a wide range of unique physical applications in open systems. In this context, the mutual interactions among four coupled states around a fourth-order EP (EP4) in a…

Optics · Physics 2020-08-19 Sibnath Dey , Arnab Laha , Somnath Ghosh

Chirality is more than a geometric curiosity; it governs measurable asymmetries across nature, from enantiomer-selective drugs and left-handed fermions in particle physics to handed charge transport in Weyl semimetals. We extend this…

Quantum Physics · Physics 2025-12-23 Kyu-Won Park , KyeongRo Kim , Kabgyun Jeong

Exceptional points (EPs), indicative of parity-time (PT) symmetry breaking, play a central role in non-Hermitian physics, yet most studies begin from deliberately engineered effective Hamiltonians whose parameters are tuned to exhibit…

Quantum Physics · Physics 2026-03-12 Eric R. Bittner , Bhavay Tyagi , Kevin E. Bassler

We demonstrate the existence of exceptional points of degeneracy (EPD) of periodic eigenstates in non-Hermitian coupled chains of dipolar scatterers. Guided modes supported by these structures can exhibit an EPD in their dispersion diagram…

Optics · Physics 2017-03-22 Mohamed A. K. Othman , Vincenzo Galdi , Filippo Capolino

Spectral degeneracies (dubbed nodal points in momentum space) play fundamental roles in understanding exotic properties of light and matter. In lattice systems, unpaired band-structure degeneracies are subject to well-established no-go…

Mesoscale and Nanoscale Physics · Physics 2026-03-30 Kunkun Wang , J. Lukas K. König , Kang Yang , Lei Xiao , Wei Yi , Emil J. Bergholtz , Peng Xue

Exceptional points in non-Hermitian systems have recently been shown to possess nontrivial topological properties, and to give rise to many exotic physical phenomena. However, most studies thus far have focused on isolated exceptional…

Optics · Physics 2019-02-21 Hengyun Zhou , Jong Yeon Lee , Shang Liu , Bo Zhen