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Bulk-boundary correspondence is the cornerstone of topological physics. In some non-Hermitian topological system this fundamental relation is broken in the sense that the topological number calculated for the Bloch energy band under the…

Mesoscale and Nanoscale Physics · Physics 2020-09-29 Ken-Ichiro Imura , Yositake Takane

The non-Hermitian models, which are symmetric under parity (P) and time-reversal (T) operators, are the cornerstone for the fabrication of new ultra-sensitive optoelectronic devices. However, providing the gain in such systems usually…

Quantum Physics · Physics 2023-03-17 Hamed Ghaemi-Dizicheh , Hamidreza Ramezani

We introduce the exceptional topological insulator (ETI), a non-Hermitian topological state of matter that features exotic non-Hermitian surface states which can only exist within the three-dimensional topological bulk embedding. We show…

Mesoscale and Nanoscale Physics · Physics 2021-10-04 M. Michael Denner , Anastasiia Skurativska , Frank Schindler , Mark H. Fischer , Ronny Thomale , Tomáš Bzdušek , Titus Neupert

Bulk-boundary correspondence is a fundamental principle for topological phases where bulk topology determines gapless boundary states. On the other hand, it has been known that corner or hinge modes in higher order topological insulators…

Mesoscale and Nanoscale Physics · Physics 2022-03-17 Takumi Bessho , Ken Mochizuki , Hideaki Obuse , Masatoshi Sato

We propose a two-dimensional non-Hermitian Chern insulator with inversion symmetry, which is anisotropic and has staggered gain and loss in both x and y directions. In this system, conventional bulk-boundary correspondence holds. The Chern…

Mesoscale and Nanoscale Physics · Physics 2019-10-11 H. C. Wu , L. Jin , Z. Song

Non-Hermitian skin-edge states emerge only at one edge in one-dimensional nonreciprocal chains, where all states are localized at the edge irrespective of eigenvalues. The bulk topological number is the winding number associated with the…

Mesoscale and Nanoscale Physics · Physics 2019-05-10 Motohiko Ezawa

We demonstrate that Hermitian, nonlocal parametric pairing processes can induce non-Hermitian topology and skin modes, offering a simple alternative to complex bath engineering. Our model, stabilized by local dissipation and operating in…

Mesoscale and Nanoscale Physics · Physics 2025-05-06 Markus Bestler , Alexander Dikopoltsev , Oded Zilberberg

The topology of non-Hermitian systems is drastically shaped by the non-Hermitian skin effect, which leads to the generalized bulk-boundary correspondence and non-Bloch band theory. The essential part in formulations of bulk-boundary…

Mesoscale and Nanoscale Physics · Physics 2019-12-11 Fei Song , Shunyu Yao , Zhong Wang

Capital to topological insulators, the bulk-boundary correspondence ties a topological invariant computed from the bulk (extended) states with those at the boundary, which are hence robust to disorder. Here we put forward an ordering unique…

Mesoscale and Nanoscale Physics · Physics 2018-03-14 V. M. Martinez Alvarez , J. E. Barrios Vargas , L. E. F. Foa Torres

Recent studies of disorder or non-Hermiticity induced topological insulators inject new ingredients for engineering topological matter. Here we consider the effect of purely non-Hermitian disorders, a combination of these two ingredients,…

Mesoscale and Nanoscale Physics · Physics 2022-12-12 Xi-Wang Luo , Chuanwei Zhang

Non-Hermitian (NH) Hamiltonians can be used to describe dissipative systems, and are currently intensively studied in the context of topology. A salient difference between Hermitian and NH models is the breakdown of the conventional…

Mesoscale and Nanoscale Physics · Physics 2020-10-14 Elisabet Edvardsson , Flore K. Kunst , Tsuneya Yoshida , Emil J. Bergholtz

Non-Hermitian systems with non-reciprocal hopping may display the non-Hermitian skin effect, where states under open boundary conditions localize exponentially at one edge of the system. This localization has been linked to spectral winding…

Disordered Systems and Neural Networks · Physics 2025-12-01 Clément Fortin , Kai Wang , T. Pereg-Barnea

The interplay between Floquet driving and non-Hermitian gain/loss could give rise to intriguing phenomena including topological funneling of light, edge-state delocalization, anomalous topological transitions and Floquet non-Hermitian skin…

Applied Physics · Physics 2026-03-17 Weiwei Zhu , Longwen Zhou , Linhu Li , Jiangbin Gong

The bulk-boundary or bulk-edge correspondence is a principle relating surface confined states to the topological classification of the bulk. By combining non-Hermitian ingredients in terms of gain or loss with media that violate…

Mesoscale and Nanoscale Physics · Physics 2020-11-18 Penglin Gao , Morten Willatzen , Johan Christensen

A striking feature of non-Hermitian systems is the presence of two different types of topology. One generalizes Hermitian topological phases, and the other is intrinsic to non-Hermitian systems, which are called line-gap topology and…

Mesoscale and Nanoscale Physics · Physics 2024-04-01 Daichi Nakamura , Takumi Bessho , Masatoshi Sato

Time-periodic driving in the form of coherent radiation provides powerful tool for the manipulation of topological materials or synthetic quantum matter. In this paper we propose a scheme to realize non-Hermitian semimetals exhibiting…

Mesoscale and Nanoscale Physics · Physics 2020-12-07 Peng He , Ze-Hao Huang

Electronic bands featuring nontrivial bulk topological invariant manifest through robust gapless modes at the boundaries, e.g., edges and surfaces. As such this bulk-boundary correspondence is also operative in driven quantum materials. For…

Mesoscale and Nanoscale Physics · Physics 2021-07-26 Tanay Nag , Bitan Roy

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…

Spectra of bulk or edges in topological insulators are often made complex by non-Hermiticity. Here, we show that symmetry protection enables entirely real spectra for both bulk and edges even in non-Hermitian topological insulators. In…

Mesoscale and Nanoscale Physics · Physics 2020-09-11 Kohei Kawabata , Masatoshi Sato

Topological insulators are insulating in the bulk but feature conducting states on their surfaces. Standard methods for probing their topological properties largely involve probing the surface, even though topological invariants are defined…