Higher-order quantum spin Hall effect in a photonic crystal

Xie, Biye; Su, Guangxu; Wang, Hongfei; Liu, Feng; Hu, Lumang; Yu, Si‐Yuan; Zhan, Peng; Lu, M.; Wang, Zhenlin; Chen, Yan‐Feng

doi:10.1038/s41467-020-17593-8

Cited by 182 publications

(87 citation statements)

References 55 publications

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“…Meanwhile, the experimental quest for higher-dimensional non-Hermitian systems is still absent. On another front, the rising of higher-order topological insulators (HOTIs) provides a realm where band topology delicately interplays with crystalline symmetries and leads to multidimensional topological physics [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58] . At the interface between the non-Hermitian physics and HOTIs, little is known in theories or experiments.…”

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confidence: 99%

Observation of higher-order non-Hermitian skin effect

et al. 2021

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Beyond the scope of Hermitian physics, non-Hermiticity fundamentally changes the topological band theory, leading to interesting phenomena, e.g., non-Hermitian skin effect, as confirmed in one-dimensional systems. However, in higher dimensions, these effects remain elusive. Here, we demonstrate the spin-polarized, higher-order non-Hermitian skin effect in two-dimensional acoustic higher-order topological insulators. We find that non-Hermiticity drives wave localizations toward opposite edges upon different spin polarizations. More interestingly, for finite systems with both edges and corners, the higher-order non-Hermitian skin effect leads to wave localizations toward two opposite corners for all the bulk, edge and corner states in a spin-dependent manner. We further show that such a skin effect enables rich wave manipulation by configuring the non-Hermiticity. Our study reveals the intriguing interplay between higher-order topology and non-Hermiticity, which is further enriched by the pseudospin degree of freedom, unveiling a horizon in the study of non-Hermitian physics.

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confidence: 99%

Observation of higher-order non-Hermitian skin effect

et al. 2021

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“…[16][17][18] Such a behavior is the key advantage over the conventional photonic structures and make them useful for the practical applications. As novel topological phases, higher-order topological insulating (HOTI) phases have recently been discovered in various quantum and classical systems, including crystalline [19] and amorphous materials, [20,21] photonic [15,16,[22][23][24][25][26][27][28][29][30][31] and phononic The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/andp.202100075 DOI: 10.1002/andp.202100075 crystals, [32][33][34][35] and electric circuits. [36,37] As one of the most well-known and simplest second-order topological insulator (SOTI), one might take the SOTI in the systems described by 2D SSH model (see, e.g., ref.…”

Section: Introductionmentioning

confidence: 99%

Second‐Order Photonic Topological Corner States in Square Lattices with Low Symmetry

Kim

2021

Annalen der Physik

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In most cases, higher‐order topological insulating phases are observed in crystalline materials and photonic/phononic crystals with high crystalline symmetries. Few exceptions include amorphous and quasi‐crystalline matters, which have recently been demonstrated to exhibit such topological phases as well. This report reveals analytically and numerically that the photonic crystals with asymmetric sublattices can also exhibit second‐order topological insulating phases. The appearance of band inversion for the change of unit cell parameters, the quantized 2D polarizations and topological corner charges, and the generation of corner states explicitly reveal the existence of such second‐order photonic topological insulating phases. Quite interestingly, for arbitrarily shaped asymmetric unit cells, second‐order topological corner states are also observed, provided that the intercell coupling dominates over the intracell one.

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“…Recently, a new class of higher-order TPCs has been extensively investigated. [39] In contrast to the TPCs with bulk-boundary correspondence, the higher-order TPCs support topological states with dimensionality two lower than the system, thereby offering us additional degrees of freedom to manipulate light flow. [40] By now, it has been observed that second-order TPCs may support 0D corner state, which is highly localized and exhibits nonradiative characteristic.…”

Section: Introductionmentioning

confidence: 99%

Manipulating Second Harmonic Generation in Higher‐Order Topological Photonic Crystals

Guo

Chen

et al. 2021

Annalen der Physik

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Higher-order topological photonic crystals (TPCs) have attracted much attention in the past several years since they do not obey the conventional bulk-boundary correspondence in topological insulating phases. This characteristic offers a new dimension with which to trap and manipulate the flow of light. In this work, 2D higher-order TPCs for engineering optical second harmonic generation (SHG) are designed. In the TPCs, a topological corner-state is achieved and it is demonstrated that the high localization of photons at the corner-state can significantly promote optical SHG. In addition, topological edge-states are obtained by breaking the Dirac degeneracy point near the SHG frequency. They are also topologically protected and immune to bending resistance. Therefore, the enhanced SHG signal from the corner-state can be manipulated precisely for transmitting through the designed interface with relatively low loss due to the topological-protection edge waves. This design strategy combines the advantages of corner-state and edge-state in higher-order TPCs, demonstrating potential applications of topological photonic devices, such as optical communication and optical computing technologies.

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Higher-order quantum spin Hall effect in a photonic crystal

Cited by 182 publications

References 55 publications

Observation of higher-order non-Hermitian skin effect

Observation of higher-order non-Hermitian skin effect

Second‐Order Photonic Topological Corner States in Square Lattices with Low Symmetry

Manipulating Second Harmonic Generation in Higher‐Order Topological Photonic Crystals

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