Observation of geometry-dependent skin effect in non-Hermitian phononic crystals with exceptional points

Zhou, Qiuyan; Wu, Jixuan; Pu, Zhenhang; Lu, Jiuyang; Huang, Xueqin; Deng, Weiyin; Ke, Manzhu; Liu, Zhengyou

doi:10.1038/s41467-023-40236-7

Cited by 36 publications

(3 citation statements)

References 55 publications

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“…However, with the recent development of non-Hermitian physics, it has been found that not only the edge modes but all the bulk states can pile up at the edges of the systems as well, and such phenomenon is dubbed as noptn-Hermitian skin effects [22][23][24][25][26][27][28][29][30][31][32][33][34][35]. In these cases, the bulk boundary modes can be extremely sensitive to local perturbations and the conventional BBC can be broken [36,37].…”

Section: Introductionmentioning

confidence: 99%

Bulk-boundary correspondence in topological systems with the momentum dependent energy shift

Wang,

Yang,

Wu-Ming Liu

2024

Quantum Sci. Technol.

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Bulk-boundary correspondence (BBC) remains the central topic in modern condensed matter physics and has received a boost of interest with the recent discovery of non-Hermitian skin effects. However, there still exist profound features of BBC that are beyond the existing framework. Here, we report the unexpected behavior of BBC when the Hamiltonian contains terms of the form d0(k)I, which serves as a momentum dependent energy shift. For Hermitian cases, the momentum dependent energy shift can force the system to be metallic, where topological phase transitions can take place with the upper and the lower bands kept untouched. The modified BBC should be reconstructed from the perspective of the indirect band gap. In non-Hermitian cases, skin effects are found to be capable of coexisting with the preserved BBC, of which the process can be greatly facilitated by the complex d0(k)I. Remarkably, such results can be led to a further step, and contrary to the intuition, the modified BBC in Hermitian systems can be restored to be conventional by including extra non-Hermiticity. The physical origin for these phenomena lies in that d0(k)I can drastically change the point gap topology. Finally, the corresponding experimental simulations are proposed via the platforms of electric circuits.

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Section: Introductionmentioning

confidence: 99%

Bulk-boundary correspondence in topological systems with the momentum dependent energy shift

Wang,

Yang,

Wu-Ming Liu

2024

Quantum Sci. Technol.

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“…Manifesting as a boundary localization of eigenstates, NHSE becomes more sophisticated in higher dimensional systems, where richer structures of boundaries emerge from different geometries [51][52][53][54][55][56][57] and defects [58][59][60][61][62] of lattices. In this topical review, we provide an overview of the discovery and developments of HSTE [63], a novel phenomenon arising from the interplay of NHSE and topological boundary states in two-or higher-dimensions.…”

Section: Introductionmentioning

confidence: 99%

A brief review of hybrid skin-topological effect

Zhu,

2024

J. Phys.: Condens. Matter

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The finding of non-Hermitian skin effect has revolutionized our understanding of non-Hermitian topological phases, where the usual bulk-boundary correspondence is broken and new topological phases specific to non-Hermitian system are uncovered. Hybrid skin-topological effect (HSTE) is a class of newly discovered non-Hermitian topological states that simultaneously supports skin-localized topological edge states and extended bulk states. Here we provide a brief review of HSTE, starting from different mechanics that have been used to realize HSTE, including non-reciprocal couplings, onsite gain/loss, and non-Euclidean lattice geometries. We also review some theoretical developments closely related to the HSTE, including the concept of higher-order non-Hermitian skin effect, parity-time symmetry engineering, and non-Hermitian chiral skin effect. Finally, we summarize recent experimental exploration of HSTE, including its realization in electric circuits systems, non-Hermitian photonic crystals, and active matter systems. We hope this review can make the concept of hybrid-skin effect clearer and inspire new finding of non-Hermitian topological states in higher dimensional systems.

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“…Consequently, even for a given E 0 , we are left with two complex variables and one complex constraint equation, whose solution is a 2D Riemann surface in the 4D space defined in (Re k x , Im k x , Re k y , Im k y ), making it challenging to handle both analytically and numerically. Secondly, the shape of OBC geometry can significantly affect the NHSE in two and higher dimensions [59,[64][65][66][67][68][69][70][71]. For instance, in the geometry-dependent skin effect [59], the NHSE disappears in square geometry but emerges in triangle geometry.…”

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confidence: 99%

The Case of Xiamen University: Sexual Harassment and Higher Education in China

Xu¹,

McCann²,

Pufpaff³

2021

Doing Good Business in China

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In this work, we propose a theory on the two-dimensional non-Hermitian skin effect by resolving two representative minimal models. Specifically, we show that for any given non-Hermitian Hamiltonian, (i) the corresponding region covered by its open boundary spectrum on the complex energy plane should be independent of the open boundary geometry; and (ii) for any given open boundary eigenvalue E0, its corresponding two-dimensional asymptotic generalized Brillouin zone is determined by a series of geometry-independent Bloch/non-Bloch Fermi points and geometry-dependent non-Bloch equal frequency contours that connect them. A corollary of our theory is that most symmetry-protected exceptional semimetals should be robust to variations in OBC geometry. Our theory paves the way to the discussion on the higher dimensional non-Bloch band theory and the corresponding non-Hermitian bulk-boundary correspondence.

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Observation of geometry-dependent skin effect in non-Hermitian phononic crystals with exceptional points

Cited by 36 publications

References 55 publications

Bulk-boundary correspondence in topological systems with the momentum dependent energy shift

Bulk-boundary correspondence in topological systems with the momentum dependent energy shift

A brief review of hybrid skin-topological effect

The Case of Xiamen University: Sexual Harassment and Higher Education in China

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