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We investigate the action of a non-invertible symmetry on spins chains whose topological lines are labelled by representations of the four-dimensional Taft algebra. The main peculiarity of this symmetry is the existence of junctions between…

Strongly Correlated Electrons · Physics 2026-01-21 Clement Delcamp , Edmund Heng , Matthew Yu

Non-Hermitian systems can host topological states with novel topological invariants and bulk-edge correspondences that are distinct from conventional Hermitian systems. Here we show that two unique classes of non-Hermitian 2D topological…

Mesoscale and Nanoscale Physics · Physics 2021-03-10 Junpeng Hou , Ya-Jie Wu , Chuanwei Zhang

We revisit the problem of classifying topological band structures in non-Hermitian systems. Recently, a solution has been proposed, which is based on redefining the notion of energy band gap in two different ways, leading to the so-called…

Mathematical Physics · Physics 2020-05-20 Charles C. Wojcik , Xiao-Qi Sun , Tomáš Bzdušek , Shanhui Fan

The complex eigenenergies and non-orthogonal eigenstates of non-Hermitian systems exhibit unique topological phenomena that cannot appear in Hermitian systems. Representative examples are the non-Hermitian skin effect and exceptional…

Quantum Physics · Physics 2025-12-19 Jung-Wan Ryu , Jae-Ho Han , Chang-Hwan Yi , Hee Chul Park , Moon Jip Park

A prominent feature of some one-dimensional non-Hermitian systems is that all right-eigenstates of the non-Hermitian Hamiltonian are localized in one end of the chain. The topological and trivial phases are distinguished by the emergence of…

Mesoscale and Nanoscale Physics · Physics 2019-07-17 Motohiko Ezawa

Non-Hermitian systems give rise to distinct topological phenomena, yet their manifestations at temporal interfaces characterized by abrupt changes in system parameters remain largely unex plored. Upon an abrupt alteration of the Hamiltonian…

Externally controllable band gap properties of a material is crucial in designing optoelectronic devices with desirable properties on-demand. Here, a possibility of single parameter tuning of trivial to non-trivial topological band gap by…

Mesoscale and Nanoscale Physics · Physics 2020-08-17 Bikashkali Midya

In this work we first show a simple approach to constructing non-Hermitian Hamiltonians with a real spectrum, which are \textit{not} obtained by a non-unitary transformation such as the imaginary gauge transformation. They are given,…

Quantum Physics · Physics 2024-03-18 Li Ge

Non-Hermiticity enriches the contents of topological classification of matter including exceptional points, bulk-edge correspondence and skin effect. Gain and loss can be described by imaginary diagonal elements in Hamiltonians and the…

Mesoscale and Nanoscale Physics · Physics 2020-07-15 X. L. Zhao , L. B. Chen , L. B. Fu , X. X. Yi

Classifications of symmetry-protected topological (SPT) phases provide a framework to systematically understand the physical properties and potential applications of topological systems. While such classifications have been widely explored…

Mesoscale and Nanoscale Physics · Physics 2019-06-12 Hengyun Zhou , Jong Yeon Lee

A fundamental dichotomous classification for all physical systems is according to whether they are spinless or spinful. This is especially crucial for the study of symmetry-protected topological phases, as the two classes have distinct…

Mesoscale and Nanoscale Physics · Physics 2021-05-13 Y. X. Zhao , Cong Chen , Xian-Lei Sheng , Shengyuan A. Yang

Symmetry is one of the cornerstones of modern physics and has profound implications in different areas. In symmetry-protected topological systems, symmetries are responsible for protecting surface states, which are at the heart of the…

Mesoscale and Nanoscale Physics · Physics 2024-05-10 E. Slootman , W. Cherifi , L. Eek , R. Arouca , E. J. Bergholtz , M. Bourennane , C. Morais Smith

The non-trivial topological features in the energy band of non-Hermitian systems provide promising pathways to achieve robust physical behaviors in classical or quantum open systems. A key topological feature, unique to non-Hermitian…

Quasi-Hermitian quantum systems, including $\mathcal{PT}$-symmetric ones, can be mapped to equivalent Hermitian systems via a similarity transformation that redefines the inner product with a positive-definite metric operator. Although an…

Quantum Physics · Physics 2026-05-12 Ming-Zhang Wang , Xu-Yang Hou , Hao Guo

For the classification of topological phases of matter, an important consideration is whether a system is spinless or spinful, as these two classes have distinct symmetry algebra that gives rise to fundamentally different topological…

Topological phases and transitions are of fundamental importance in physics, which provide a deep insight into the understanding of materials. Recently, non-Abelian topological transitions have been investigated in Hermitian systems,…

Quantum Physics · Physics 2025-03-25 Yunhan Wang , Yang Wu , Xiangyu Ye , Chang-Kui Duan , Ya Wang , Haiping Hu , Xing Rong , Jiangfeng Du

Symmetry plays a key role in modern physics, as manifested in the revolutionary topological classification of matter in the past decade. So far, we seem to have a complete theory of topological phases from internal symmetries as well as…

Mesoscale and Nanoscale Physics · Physics 2022-03-23 Haoran Xue , Zihao Wang , Yue-Xin Huang , Zheyu Cheng , Letian Yu , Y. X. Foo , Y. X. Zhao , Shengyuan A. Yang , Baile Zhang

The interplay between topology and quantum criticality has given rise to the notion of symmetry-enriched criticality, which has attracted considerable attention in recent years. In this Letter, we demonstrate that parity time (PT) symmetry…

Quantum Physics · Physics 2026-05-15 Kuang-Hung Chou , Xue-Jia Yu , Po-Yao Chang

The Hofstadter model exemplifies a large class of physical systems characterized by particles hopping on a lattice immersed in a gauge field. Recent advancements on various synthetic platforms have enabled highly-controllable simulations of…

Mesoscale and Nanoscale Physics · Physics 2022-09-15 Yi Yang , Hoi Chun Po , Vincent Liu , John D. Joannopoulos , Liang Fu , Marin Soljačić

Quantum devices characterized by non-Hermitian topology are predicted to show highly robust and potentially useful properties, but realizing them has remained a daunting experimental task. This is because non-Hermiticity is often associated…