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In many classical and quantum systems described by an effective non-Hermitian Hamiltonian, spectral phase transitions, from an entirely real energy spectrum to a complex spectrum, can be observed as a non-Hermitian parameter in the system…

Quantum Physics · Physics 2023-02-22 Stefano Longhi , Liang Feng

We show that a Dicke-type pseudo-hermitian Hamiltonian undergoes quantum phase transition by mapping it to the "Dressed Dicke Model" through a similarity transformation. We find the positive-definite metric in the Hilbert space of the…

Quantum Physics · Physics 2009-08-14 Tetsuo Deguchi , Pijush K. Ghosh

We study quantum phases and phase transitions in a one-dimensional interacting fermion system with a Lieb-Schultz-Mattis (LSM) type anomaly. Specifically, the inversion symmetry enforces any symmetry-preserving gapped ground state of the…

Strongly Correlated Electrons · Physics 2022-03-14 Wayne Zheng , D. N. Sheng , Yuan-Ming Lu

We study the quantum phase transition (QPT) in a non-Hermitian Tavis-Cummings (TC) model of experimentally accessible parameters, which is engineered with two drive fields applied to an ensemble of two-level systems (TLSs) and a cavity,…

Quantum Physics · Physics 2020-09-15 Guo-Qiang Zhang , Zhen Chen , J. Q. You

A crowd of nonequilibrium entities can show phase transition behaviors that are prohibited in conventional equilibrium setups. An interesting question is whether similar activity-driven phase transitions also occur in pure quantum systems.…

Statistical Mechanics · Physics 2022-06-28 Kyosuke Adachi , Kazuaki Takasan , Kyogo Kawaguchi

The assumption that quantum systems relax to a stationary state in the long-time limit underpins statistical physics and much of our intuitive understanding of scientific phenomena. For isolated systems this follows from the eigenstate…

Quantum Physics · Physics 2019-04-16 Berislav Buca , Joseph Tindall , Dieter Jaksch

In closed quantum systems, a dynamical phase transition is identified by nonanalytic behaviors of the return probability as a function of time. In this work, we study the nonunitary dynamics following quenches across exceptional points in a…

Statistical Mechanics · Physics 2018-08-29 Longwen Zhou , Qing-hai Wang , Hailong Wang , Jiangbin Gong

The discovery of topological phases in non-Hermitian open classical and quantum systems challenges our current understanding of topological order. Non-Hermitian systems exhibit unique features with no counterparts in topological Hermitian…

Mesoscale and Nanoscale Physics · Physics 2019-06-26 Stefano Longhi

An exactly solvable Kitaev model in a two-dimensional square lattice exhibits a topological quantum phase transition which is different from the symmetry-breaking transition at zero temperature. When the ground state of a nonlinearly…

Quantum Physics · Physics 2025-03-11 Leela Ganesh Chandra Lakkaraju , Sudip Kumar Haldar , Aditi Sen De

A quantum system can undergo a continuous phase transition at the absolute zero of temperature as some parameter entering its Hamiltonian is varied. These transitions are particularly interesting for, in contrast to their classical finite…

Condensed Matter · Physics 2009-10-28 S. L. Sondhi , S. M. Girvin , J. P. Carini , D. Shahar

We establish a unified framework for dynamical quantum phase transitions (DQPTs) in non-Hermitian systems that encompasses both biorthogonal and self-norm non-biorthogonal formulations for pure and mixed states under quantum quench…

Quantum Physics · Physics 2025-10-27 Yongxu Fu , Gao Xianlong

A conventional quantum phase transition (QPT) occurs not only at zero temperature, but also exhibits finite-temperature quantum criticality. Motivated by the discovery of the pseudo-Hermiticity of non-Hermitian systems, we explore the…

Quantum Physics · Physics 2015-12-09 Ci. Li , Zhi. Song

Dynamical quantum phase transitions in non-Hermitian systems pose fundamental challenges due to the intrinsic biorthogonality of their eigenstates. In this work, we extend a biorthogonal framework to investigate dynamical quantum phase…

Quantum Physics · Physics 2026-05-26 Haoran Gu , Yubo Zhao , Siyuan Cheng , Yuee Xie , Xiaosen Yang , Yuanping Chen

Spontaneous breaking of continuous time translation symmetry into a discrete one is related to time crystal formation. While the phenomenon is not possible in the ground state of a time-independent many-body system, it can occur in an…

Quantum Gases · Physics 2018-08-21 Arkadiusz Kosior , Andrzej Syrwid , Krzysztof Sacha

A conventional quantum phase transition (QPT) can be accessed by varying a real parameter at absolute zero temperature. Motivated by the discovery of the pseudo-Hermiticity of non-Hermitian systems, we explore the QPT in non-Hermitian…

Quantum Physics · Physics 2014-07-16 C. Li , G. Zhang , X. Z. Zhang , Z. Song

Unraveling the mechanisms of ergodicity breaking in complex quantum systems is a central pursuit in nonequilibrium physics. In this work, we investigate a one-dimensional spin model featuring a tunable long-range hopping term, $H_{n}$,…

Quantum Physics · Physics 2025-12-17 Y. S. Liu , X. Z. Zhang

We study an entanglement phase transition in a class of chaotic non-Hermitian spin chains whose spin-spin coupling terms commute with the non-Hermitian contributions. Two representative models are investigated: the transverse-field Ising…

Quantum Physics · Physics 2026-04-30 Zhen-Tao Zhang , Feng Mei

We derive a new time-dependent Schr\"odinger equation(TDSE) for quantum models with non-hermitian Hamiltonian. Within our theory, the TDSE is symmetric in the two Hilbert spaces spanned by the left and the right eigenstates, respectively.…

Quantum Physics · Physics 2017-02-24 Ye Xiong , Peiqing Tong

Critical phase transitions contain a variety of deep and universal physics, and are intimately tied to thermodynamic quantities through scaling relations. Yet, these notions are challenged in the context of non-Hermiticity, where spatial or…

Statistical Mechanics · Physics 2021-01-06 R. Arouca , C. H. Lee , C. Morais Smith

Phase transitions, non-Hermiticity and nonreciprocity play central roles in fundamental physics. However, the triple interplay of these three fields is of lack in the quantum domain. Here, we show nonreciprocal parity-time-symmetric phase…

Quantum Physics · Physics 2024-04-23 Miao Cai , Jiang-Shan Tang , Ming-Yuan Chen , Keyu Xia