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Non-Hermitian systems, going beyond conventional Hermitian systems, have brought in intriguing concepts such as exceptional points and complex spectral topology as well as exotic phenomena such as non-Hermitian skin effects (NHSEs).…

Quantum Physics · Physics 2024-09-23 Li-Wei Wang , Jian-Hua Jiang

We study quantum phase transitions in non-Hermitian XY and transverse-field Ising spin chains, in which the non-Hermiticity arises from the imaginary magnetic field. Analytical and numerical results show that at exceptional points,…

Quantum Physics · Physics 2015-06-10 Ci. Li , Zhi. Song

The exotic physics emerging in non-Hermitian systems with balanced distributions of gain and loss has drawn a great deal of attention in recent years. These systems exhibit phase transitions and exceptional point singularities in their…

Optics · Physics 2021-03-17 Arik Bergman , Robert Duggan , Kavita Sharma , Moshe Tur , Avi Zadok , Andrea Alu

Exceptional points associated with non-hermitian operators, i.e. operators being non-hermitian for real parameter values, are investigated. The specific characteristics of the eigenfunctions at the exceptional point are worked out. Within…

Quantum Physics · Physics 2009-11-10 W. D. Heiss

One of the most fascinating and puzzling aspects of non-Hermitian systems is their spectral degeneracies, i.e., exceptional points (EPs), at which both eigenvalues and eigenvectors coalesce to form a defective state space. While coupled…

Mesoscale and Nanoscale Physics · Physics 2023-03-08 Kuangyin Deng , Xin Li , Benedetta Flebus

Exceptional points (EPs) in anti-parity-time (APT)-symmetric systems have attracted significant interest. While linear APT-symmetric systems exhibit structural similarities with nonlinear dissipative systems, such as mutually…

Optics · Physics 2025-09-03 Takahiro Uemura , Kenta Takata , Masaya Notomi

The dynamical quantum phase transition is characterized by the emergence of nonanalytic behaviors in the rate function, corresponding to the occurrence of exact zero points of the Loschmidt echo in the thermodynamical limit. In general,…

Quantum Physics · Physics 2023-04-12 Yumeng Zeng , Bozhen Zhou , Shu Chen

Non-Hermitian physics is reshaping our understanding of quantum systems by revealing states and phenomena without Hermitian counterparts. While non-Hermiticity is typically associated with gain-loss processes in open systems, we uncover a…

Materials Science · Physics 2025-12-17 Enrico Perfetto , Gianluca Stefanucci

The appearance of so-called exceptional points in the complex spectra of non-Hermitian systems is often associated with phenomena that contradict our physical intuition. One example of particular interest is the state-exchange process…

We conduct a numerical study of wave localization in disordered three-dimensional non-Hermitian systems featuring exceptional points. The energy spectrum of a disordered non-Hermitian Hamiltonian, exhibiting both parity-time and…

Disordered Systems and Neural Networks · Physics 2025-09-30 C. Wang , X. R. Wang

Exceptional points are singularities in the spectrum of non-Hermitian systems in which several eigenvectors are linearly dependent and their eigenvalues are equal to each other. Usually it is assumed that the order of the exceptional point…

Quantum Physics · Physics 2025-12-11 Timofey T. Sergeev , Evgeny S. Andrianov , Alexander A. Zyablovsky

Non-Hermitian skin effects and exceptional points are topological phenomena characterized by integer winding numbers. In this study, we give methods to theoretically detect skin effects and exceptional points by generalizing inversion…

Mesoscale and Nanoscale Physics · Physics 2021-05-24 Ryo Okugawa , Ryo Takahashi , Kazuki Yokomizo

We show that non-Hermitian biorthogonal many-body phase transitions can be characterized by the enhanced decay of Loschmidt echo. The quantum criticality is numerically investigated in a non-Hermitian transverse field Ising model by…

Strongly Correlated Electrons · Physics 2023-01-13 Jia-Chen Tang , Su-Peng Kou , Gaoyong Sun

Non-Hermitian (NH) systems provide a fertile platform for quantum technologies, owing in part to their distinct dynamical phases. These systems can be characterized by the preservation or spontaneous breaking of parity-time reversal…

Non-Hermitian systems and their topological singularities, such as exceptional points (EPs), lines, and surfaces, have recently attracted intense interest. The investigation of these exceptional constituents has led to fruitful…

Optics · Physics 2024-08-08 Liang Fang , Kai Bai , Cheng Guo , Tian-Rui Liu , Jia-Zheng Li , Meng Xiao

The non-analyticity induced by exceptional points (EPs) has manifestations not only in non-Hermitian but also in Hermitian systems. In this work, we focus on a minimal Hermitian bosonic Kitaev model to reveal the dynamical demonstration of…

Quantum Physics · Physics 2025-12-02 D. K. He , Z. Song

When sources of energy gain and loss are introduced to a wave-scattering system, the underlying mathematical formulation will be non-Hermitian. This paves the way for the existence of exceptional points, where eigenmodes are linearly…

Analysis of PDEs · Mathematics 2021-03-15 Habib Ammari , Bryn Davies , Erik Orvehed Hiltunen , Hyundae Lee , Sanghyeon Yu

Exceptional points, the spectral degeneracy points in the complex parameter space, are fundamental to non-Hermitian quantum systems. The dynamics of non-Hermitian systems in the presence of exceptional points differ significantly from those…

Quantum Physics · Physics 2021-01-29 Chon-Fai Kam , Yang Chen

We demonstrate the existence of a dynamical quantum phase transition (DQPT) in a dissipative collective-spin model that exhibits the boundary time crystal (BTC) phase. We initialize the system in the ground state of the Hamiltonian in…

Quantum Physics · Physics 2026-02-05 Sukrut Mondkar , Priya Ghosh , Ujjwal Sen

Exceptional points in an optical dimer of spheres, which have the same size and operate in the spectral region of the dipolar resonance, are considered. By choosing different materials of these spheres, we can offset the radiative loss and…

Optics · Physics 2023-07-31 Alexey A. Dmitriev , Mikhail V. Rybin