Valley Physics in Non-Hermitian Artificial Acoustic Boron Nitride

Wang, Mudi; Ye, Liping; Christensen, Johan; Liu, Zhengyou

doi:10.1103/physrevlett.120.246601

Cited by 88 publications

(44 citation statements)

References 56 publications

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“…Realized in acoustics, the scheme is further understood through a general tight-binding model, and is potential to inspire construction and utilization of type-II DPs in other research areas, such as electronic materials and coupled photonic waveguides, which may lead to exotic phenomena and properties. The deterministic scheme may serve as a platform for investigating classical topological phenomena in the context of type-II DPs, including the Klein tunneling [23,24], the Zitterbewegung effect [25][26][27], synthetic Landau levels [34] and non-Hermitian physics [31]. It may also inspire more systematic designs for type-II WPs in 3D space.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast, type-I DPs are guaranteed to exist at corners of the first Brillouin zone (FBZ) using triangular, honeycomb, or kagome lattices [22]. This property serves as a basis for further researches of many (pseudo)relativistic and topological phenomena associated with type-I DPs, such as the Klein tunneling [23,24], the Zitterbewegung effect [25][26][27], and various topological insulators [28][29][30][31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

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Deterministic Scheme for Two-Dimensional Type-II Dirac Points and Experimental Realization in Acoustics

Zhang

et al. 2020

Phys. Rev. Lett.

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Low-energy electrons near Dirac/Weyl nodal points mimic massless relativistic fermions. However, as they are not constrained by Lorentz invariance, they can exhibit tipped-over type-II Dirac/Weyl cones which provide highly anisotropic physical properties and responses, creating unique possibilities. Recently, they have been observed in several quantum and classical systems. Yet, there is still no simple and deterministic strategy to realize them since their nodal points are accidental degeneracies, unlike symmetry-guaranteed type-I counterparts. Here, we propose a band-folding scheme for constructing type-II Dirac points, and we use a tight-binding analysis to unveil its generality and deterministic nature. Through a realization in acoustics, type-II Dirac points are experimentally visualized and investigated using near-field mappings. As a direct effect of tipped-over Dirac cones, strongly tilted kink states originating from their valley-Hall properties are also observed. This deterministic scheme may serve as a basis for further investigations of intriguing physics associated with type-II Dirac/Weyl points.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Deterministic Scheme for Two-Dimensional Type-II Dirac Points and Experimental Realization in Acoustics

Zhang

et al. 2020

Phys. Rev. Lett.

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“…Since then, tremendous attention has been drawn to the field of classical analogues of electronic topological insulators in photonics, phononics, and mechanics systems. Recently, various schemes for realizing topological acoustic transport were proposed to construct pesudospin/valley degrees of freedom in two-dimensional (2D) static systems, which are passive and not time-varying, to mimicking the quantum spin/valley Hall effects [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. However, these reported pesudospin/valley-based acoustic topological insulators are still not strictly robust in oneway topological transport, since the bosonic-like time-reversal symmetry in the linear and static acoustic system does not allow any Kramers doublet [22].…”

Section: Introductionmentioning

confidence: 99%

Chirality-assisted three-dimensional acoustic Floquet lattices

Peng

Shen

et al. 2019

Phys. Rev. Research

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Artificial topological insulators in classical systems are thriving, especially the meta-atom-based threedimensional (3D) topological lattices. Here we propose a paradigm based on engineering coupling networks in a generalized spatial Floquet lattice, which gives rise to low-loss and broadband 3D topological systems. A mapping between time and space dimensions is utilized to construct the Floquet system with chirality-assisted coupling patterns periodically modulated in spatial dimensions. The cyclotron orbiting motion of sound in the bulk and reversely orbiting motion on the surface are demonstrated, which provides a direct acoustic analogue of the electronic transport in Chern insulators. Weyl points and Fermi arc-like surface states unveil the topological transport of edge states. Splicing together two Floquet lattices with opposite chirality, we realize low-loss topological negative refraction on the surface, where the mirror reflection at the interface is prohibited. Our findings provide diverse ways to construct 3D devices with topological functionalities in acoustics and beyond.

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“…The topological insulators (TIs) of photons and phonons were firstly realized in the broken time-reverse symmetry systems, in which the counterpropagating partners are perfectly prohibited [4][5][6][7][8][9][10][11][12] . Then, the quantum valley Hall effects [13][14][15][16][17][18][19][20][21] and the quantum spin Hall effects [22][23][24][25][26][27][28] were observed in time-reverse invariant photonic and phononic systems. These topological characteristics, dictated by integer topological invariants and Berry's phases of bulk energy bands, obey the bulk-edge correspondence principle, exhibiting the topologically protected gapless 1D edge states which immunize against large confined imperfectness and even spontaneous emissions.…”

mentioning

confidence: 99%

Elastic Higher-Order Topological Insulator with Topologically Protected Corner States

et al. 2019

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Topologically gapless edge states, characterized by topological invariants and Berry's phases of bulk energy bands, provide amazing techniques to robustly control the reflectionless propagation of electrons, photons and phonons. Recently, a new family of topological phases, dictated by the bulk polarization, has been observed, leading to the discovery of the higher-order topological insulators (HOTIs). So far, the HOTIs are only demonstrated in discrete mechanical and electromagnetic systems and electrical circuits with the quantized quadrupole polarization.Here, we realize the higher-order topological states in a two-dimensional (2D) continuous elastic system whose energy bands can be well described. We experimentally observe the gapped onedimensional (1D) edge states, the trivially gapped zero-dimensional (0D) corner states and the topologically protected 0D corner states. Compared with the trivial corner modes, the topological ones, immunizing against defects, are robustly localized at the obtuse-angled but not the acuteangled corners. The topological shape-dependent corner states open a new route for the design of the topologically-protected but reconfigurable 0D local eigenmodes and provide an excellent platform for the topological transformation of elastic energy among 2D bulk, 1D edge and 0D corner modes.

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Valley Physics in Non-Hermitian Artificial Acoustic Boron Nitride

Cited by 88 publications

References 56 publications

Deterministic Scheme for Two-Dimensional Type-II Dirac Points and Experimental Realization in Acoustics

Deterministic Scheme for Two-Dimensional Type-II Dirac Points and Experimental Realization in Acoustics

Chirality-assisted three-dimensional acoustic Floquet lattices

Elastic Higher-Order Topological Insulator with Topologically Protected Corner States

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