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We construct a generic two-band model which can describe topological Weyl semimetals with multiple closed Weyl loops. All the existing multi-Weyl-loop semimetals including the nodal-net, or nodal-chain and Hopf-link states can be examined…

Mesoscale and Nanoscale Physics · Physics 2018-04-25 Yao Zhou , Feng Xiong , Xiangang Wan , Jin An

The interplay between non-Hermiticity and topology opens an exciting avenue for engineering novel topological matter with unprecedented properties. While previous studies have mainly focused on one-dimensional systems or Chern insulators,…

Mesoscale and Nanoscale Physics · Physics 2021-05-12 Junpeng Hou , Ya-Jie Wu , Chuanwei Zhang

Non-Hermitian systems can exhibit extraordinary sensitivity to boundary conditions. Given that topological boundary modes and non-Hermitian skin effects can either coexist or individually appear in non-Hermitian systems, it is of great…

Quantum Physics · Physics 2024-02-27 Xintong Zhang , Jing Li

The hallmark of symmetry-protected topological (SPT) phases is the existence of anomalous boundary states, which can only be realized with the corresponding bulk system. In this work, we show that for every Hermitian anomalous boundary mode…

Mesoscale and Nanoscale Physics · Physics 2019-11-20 Jong Yeon Lee , Junyeong Ahn , Hengyun Zhou , Ashvin Vishwanath

Non-Hermitian systems exhibit richer topological properties compared to their Hermitian counterparts. It is well known that non-Hermitian systems have been classified based on either the symmetry relations for non-Hermitian Hamiltonians or…

Mesoscale and Nanoscale Physics · Physics 2024-06-11 Zhiyu Jiang , Ryo Okamoto , Hideaki Obuse

We study non-interacting electrons in disordered one-dimensional materials which exhibit a spectral gap, in each of the ten Altland-Zirnbauer symmetry classes. We define an appropriate topology on the space of Hamiltonians so that the…

Mathematical Physics · Physics 2023-07-04 Jui-Hui Chung , Jacob Shapiro

It was known that for non-Hermitian topological systems due to the non-Hermitian skin effect, the bulk-edge correspondence is broken down. In this paper, by using one-dimensional Su-SchriefferHeeger model and two-dimensional (deformed)…

Mesoscale and Nanoscale Physics · Physics 2020-05-20 Can Wang , Xiao-Ran Wang , Cui-Xian Guo , Su-Peng Kou

The non-Hermitian skin effect, nonreciprocity-induced anomalous localization of an extensive number of eigenstates, represents a hallmark of non-Hermitian topological systems with no analogs in Hermitian systems. Despite its significance…

Mesoscale and Nanoscale Physics · Physics 2025-09-22 Kohei Kawabata , Daichi Nakamura

Topological insulators exhibit boundary states protected by bulk band topology, a principle first established in quantum systems and later extended to classical waves, including phononics. Conventionally, an $n$-dimensional bulk with…

Mesoscale and Nanoscale Physics · Physics 2025-11-26 Joel R. Pyfrom , Kai Sun , Jihong A. Ma

In two-dimensional anomalous Floquet insulators, non-Hermitian boundary state engineering can be used to completely separate chiral boundary states from bulk bands in the quasienergy spectrum. The topological properties of such spectrally…

Mesoscale and Nanoscale Physics · Physics 2020-09-07 Bastian Höckendorf , Andreas Alvermann , Holger Fehske

In two dimensions, Hermitian lattices with non-zero Chern numbers and non-Hermitian lattices with a higher-order skin effect (HOSE) bypass the constraints of the Nielsen-Ninomiya no-go theorem at their one-dimensional boundaries. This…

Mesoscale and Nanoscale Physics · Physics 2025-05-22 Yifan Wang , Wladimir A. Benalcazar

Non-Hermiticity appears ubiquitously in various open classical and quantum systems and enriches classification of topological phases. However, the role of nonsymmorphic symmetry, crystalline symmetry accompanying fractional lattice…

Mesoscale and Nanoscale Physics · Physics 2025-04-30 Daichi Nakamura , Yutaro Tanaka , Ken Shiozaki , Kohei Kawabata

Topological phases have recently witnessed a rapid progress in non-Hermitian systems. Here we study a one-dimensional non-Hermitian Aubry-Andr\'e-Harper model with imaginary periodic or quasiperiodic modulations. We demonstrate that the…

Mesoscale and Nanoscale Physics · Physics 2020-06-11 Qi-Bo Zeng , Yan-Bin Yang , Yong Xu

Non-Hermiticity gives rise to unique topological phases that have no counterparts in Hermitian systems. Such intrinsic non-Hermitian topological phases appear even in one dimension while no topological phases appear in one-dimensional…

Strongly Correlated Electrons · Physics 2022-04-20 Kohei Kawabata , Ken Shiozaki , Shinsei Ryu

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

Magnetically doped topological insulators (TIs) exhibit two distinct phases: the quantum anomalous Hall (QAH) phase when the Fermi level resides within the surface gap, and a metallic phase outside the gap. The QAH phase hosts…

Mesoscale and Nanoscale Physics · Physics 2025-10-02 Le Yi , Emma Steinebronn , Asmaul Smitha Rashid , Nitin Samarth , Ramy El-Ganainy , Sahin L. Ozdemir , Morteza Kayyalha

In this work we consider a generalization of the symmetry classification of topological insulators to non-Hermitian Hamiltonians which satisfy a combined $PT$-symmetry (parity and time-reversal). We show via examples, and explicit bulk and…

Other Condensed Matter · Physics 2013-05-29 Yi Chen Hu , Taylor L. Hughes

Non-Hermitian topological phases have gained immense attention due to their potential to unlock novel features beyond Hermitian bounds. PT-symmetric (Parity Time-reversal symmetric) non-Hermitian models have been studied extensively over…

Mesoscale and Nanoscale Physics · Physics 2025-04-08 Chakradhar Rangi , Ka-Ming Tam , Juana Moreno

Higher-order topological insulators (HOTI) are a novel topological phase beyond the framework of the conventional bulk-boundary correspondence. In these peculiar systems, the topologically nontrivial boundary modes are characterized by a…

The recent discovery of topological insulators has revived interest in the topological properties of insulating band structures. In this work, we extend the topological classification of insulating band structures to include certain point…

Materials Science · Physics 2011-03-15 Liang Fu
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