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We study the skin effect in a one-dimensional system of finitely many subwavelength resonators with a non-Hermitian imaginary gauge potential. Using Toeplitz matrix theory, we prove the condensation of bulk eigenmodes at one of the edges of…

Analysis of PDEs · Mathematics 2023-06-28 Habib Ammari , Silvio Barandun , Jinghao Cao , Bryn Davies , Erik Orvehed Hiltunen

Periodically driven systems intertwined with non-Hermiticity opens a rich arena for topological phases that transcend conventional Hermitian limits. The physical significance of these phases hinges on obtaining the topological invariants…

Mesoscale and Nanoscale Physics · Physics 2026-01-23 Koustav Roy , Dipendu Halder , Koustabh Gogoi , B. Tanatar , Saurabh Basu

The non-Hermitian skin effect, as a unique feature of non-Hermitian systems, will break the topological energy braiding of the Bloch bands in open boundary systems. Going beyond the Bloch band theory, we unveil the energy braiding of the…

Mesoscale and Nanoscale Physics · Physics 2023-10-20 Yang Li , Xiang Ji , Yuanping Chen , Xiaohong Yan , Xiaosen Yang

The nature of complex eigenenergy enables unique band topology to the non-Hermitian (NH) lattice systems. Recently, there has been a fast growing interest in the elusive winding and braiding topologies of the NH single and double bands,…

Mesoscale and Nanoscale Physics · Physics 2022-12-16 Qicheng Zhang , Luekai Zhao , Xun Liu , Xiling Feng , Liwei Xiong , Wenquan Wu , Chunyin Qiu

In this work, we discuss a non-Hermitian system described via a one-dimensional single-particle tight-binding model, where the non-Hermiticity is governed by random nearest-neighbour tunnellings, such that the left-to-right and…

Disordered Systems and Neural Networks · Physics 2026-01-19 Aitijhya Saha , Debraj Rakshit

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…

Topological features embedded in ancient braiding and knotting arts endow significant impacts on our daily life and even cutting-edge science. Recently, fast growing efforts are invested to the braiding topology of complex Bloch bands in…

Mesoscale and Nanoscale Physics · Physics 2023-01-18 Qicheng Zhang , Yitong Li , Huanfa Sun , Xun Liu , Luekai Zhao , Xiling Feng , Xiying Fan , Chunyin Qiu

Hyperbolic lattices are starting to be explored in search of novel phases of matter. At the same time, non-Hermitian physics has come to the forefront in photonic, optical, phononic, and condensed matter systems. In this work, we introduce…

Mesoscale and Nanoscale Physics · Physics 2024-04-30 Nisarg Chadha , Awadhesh Narayan

We use the generalized Bloch theorem formalism of Alase {\it et al.} [{\it Phys. Rev. Lett.} {\bf 117} 076804 (2016)] to analyze simple one-dimensional tight-binding lattice systems connected by Hermitian bonds (all with the same hopping…

Mesoscale and Nanoscale Physics · Physics 2025-08-13 Balázs Hetényi , Balázs Dóra

Recently, it has been observed that the Floquet-Bloch transform with real quasiperiodicities fails to capture the spectral properties of non-reciprocal systems. The aim of this paper is to introduce the notion of a generalised Brillouin…

Mathematical Physics · Physics 2024-08-12 Habib Ammari , Silvio Barandun , Ping Liu , Alexander Uhlmann

We illuminate the fundamental mechanism responsible for the transition between the non-Hermitian skin effect and defect-induced localization in the bulk. We study a Hamiltonian with non-reciprocal couplings that exhibits the skin effect…

Mesoscale and Nanoscale Physics · Physics 2024-03-20 Bryn Davies , Silvio Barandun , Erik Orvehed Hiltunen , Richard V. Craster , Habib Ammari

In recent years, non-Hermitian phases in classical and quantum systems have garnered significant attention. In particular, their intriguing band geometry offers a platform for exploring unique topological states and unconventional quantum…

Mesoscale and Nanoscale Physics · Physics 2023-10-10 Ayan Banerjee , Arka Bandyopadhyay , Ronika Sarkar , Awadhesh Narayan

Periodically driven non-Hermitian systems can exhibit rich topological band structure and non-Hermitian skin effect, without analogs in their static or Hermitian counterparts. In this work we investigate the exceptional band-touching points…

Mesoscale and Nanoscale Physics · Physics 2020-01-22 Xizheng Zhang , Jiangbin Gong

We proposed a framework for the topological classification of non-Hermitian systems. Different from previous $K$-theoretical approaches, our approach is a homotopy classification, which enables us to see more topological invariants.…

Mesoscale and Nanoscale Physics · Physics 2022-06-09 Zhi Li , Roger S. K. Mong

The spectral and transport properties of a non-Hermitian tight-binding lattice with unidirectional hopping are theoretically investigated in three different geometrical settings. It is shown that, while for the infinitely-extended (open)…

Quantum Physics · Physics 2014-05-21 Stefano Longhi

In this paper, we review our non-Bloch band theory in one-dimensional non-Hermitian tight-binding systems. In our theory, it is shown that in non-Hermitian systems, the Brillouin zone is determined so as to reproduce continuum energy bands…

Mesoscale and Nanoscale Physics · Physics 2020-11-26 Kazuki Yokomizo , Shuichi Murakami

Non-equilibrium phases of matter have attracted much attention in recent years, among which the Floquet phase is a hot point. In this work, based on the Periodic driving Non-Hermitian model, we reveal that the winding number calculated in…

Quantum Physics · Physics 2022-09-07 Gang-Feng Guo , Yan Wang , Xi-Xi Bao , Lei Tan

Bulk-boundary correspondence, connecting the bulk topology and the edge states, is an essential principle of the topological phases. However, the bulk-boundary correspondence is broken down in general non-Hermitian systems. In this paper,…

Mesoscale and Nanoscale Physics · Physics 2021-02-24 Yang Cao , Yang Li , Xiaosen Yang

We study a non-Hermitian extension of the Creutz ladder with generic non-reciprocal hopping. By mapping the ladder onto two decoupled non-Hermitian Su--Schrieffer--Heeger (SSH) chains, we uncover a rich structure in parameter space under…

Quantum Physics · Physics 2025-12-24 Debashish Dutta , Sayan Choudhury

Unraveling real eigenfrequencies in non-Hermitian $\mathcal{PT}$-symmetric Hamiltonians has opened new avenues in quantum physics, photonics, and most recently, phononics. However, the existing literature squarely focuses on exploiting such…

Classical Physics · Physics 2022-10-07 M. Moghaddaszadeh , M. A. Attarzadeh , A. Aref , M. Nouh