Topological Valley Transport in Two-dimensional Honeycomb Photonic Crystals

Yang, Yuting; Jiang, Hua; Hang, Zhi Hong

doi:10.1038/s41598-018-20001-3

Cited by 77 publications

(70 citation statements)

References 40 publications

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“…It should be mentioned that there are different ways to break the inversion symmetry in order to open a gap at the K point of graphene/graphene-like structures. For example, in graphene/graphene-like systems, the inversion symmetry can be broken by introducing difference in A, B sublattices, such as, bianisotropic responses [23], refractive index [24], cylinder sizes [25], masses [26], bilayer designs [28], acoustic cavities [30], etc. However, in this paper we are interested in the case of breaking Dirac points by loading resonators to the junctions, which leads to interesting edge/interface waves in the corresponding gaps when boundaries are considered.…”

Section: Graphene Network Loaded With Hrsmentioning

confidence: 99%

“…The honeycomb tight-binding model with a broken inversion (sub-lattice) symmetry of the unit cell is known to possess a quantum valley Hall (QVH) topological phase transition [22,23], and the corresponding valley-protected edge states have been shown to persist under particular types of imperfections [24][25][26][27]. To observe these phenomena in acoustics, different theoretical proposals and experimental demonstrations have been reported, such as a bilayer design of sonic crystal [28], a triangular sonic crystal [29], a graphene-like structure with cavities [30] and a subwavelength honeycomb lattice [31].…”

Section: Introductionmentioning

confidence: 99%

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Acoustic graphene network loaded with Helmholtz resonators: a first-principle modeling, Dirac cones, edge and interface waves

et al. 2020

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In this work, we study the propagation of sound waves in a honeycomb waveguide network loaded with Helmholtz resonators (HRs). By using a plane wave approximation in each waveguide we obtain a first-principle modeling of the network, which is an exact mapping to the graphene tight-binding Hamiltonian. We show that additional Dirac points appear in the band diagram when HRs are introduced at the network nodes. It allows to break the inversion (sub-lattice) symmetry by tuning the resonators, leading to the appearence of edge modes that reflect the configuration of the zigzag boundaries. Besides, the dimerization of the resonators also permits the formation of interface modes located in the band gap, and these modes are found to be robust against symmetry preserving defects. Our results and the proposed networks reveal the additional degree of freedom bestowed by the local resonance in tuning the properties of not only acoustical graphene-like structures but also of more complex systems.

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Section: Graphene Network Loaded With Hrsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Acoustic graphene network loaded with Helmholtz resonators: a first-principle modeling, Dirac cones, edge and interface waves

et al. 2020

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“…Figures 1a-c gives transverse-electric (TE) polarization band structures of photonic crystals. [40][41][42] Benefitting from flexible control of building blocks, the frequency of point will go to lower extremum with finely tuning the radius of perturbed rod, enabling us to manipulate the extrema with ternary states. Such gapless band structure is protected by C 6v point group symmetry.…”

Section: Photonic Crystals With Ternary-k Band Extremamentioning

confidence: 99%

“…Inspired by antennas theory in mircowave system, [41,42,44] we set up a TAA to mimic the phase different sources. It is interesting to individually divide each extremum mode.…”

Section: Design and Analysis Of Three-antenna Array Sourcesmentioning

confidence: 99%

“…[34][35][36][37][38][39] For example, in valley photonic crystals, the binary states at K/K (different wavevectors) are locked to a pair of valley pseudospins with OAM-like phase vortex. [40][41][42] Similarly, it is easy to use a monopole-phase source to individually excite the zone-center extremum. [40][41][42] Similarly, it is easy to use a monopole-phase source to individually excite the zone-center extremum.…”

Section: Introductionmentioning

confidence: 99%

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Selective Excitation of Band Extrema in Valley Photonic Crystals

Yuan

Zhao

et al. 2019

Annalen der Physik

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Flexible control of building blocks of photonic crystals enables achieving desirable band structures. Exploration of photonic band extrema has brought many fantastic features to design artificial optical materials, such as Brillouin-zone-corner extrema for valley photonic materials and zone-center extremum for zero-index metamaterials. However, two such kinds of extrema are always found independently in different photonic crystals. In this work, a kind of valley photonic crystals possessing both zone-center and zone-corner band extrema almost at the same frequency is proposed. Inspired by antennas theory, a three-antenna array (TAA) source is devoted to individually manipulate each extremum. The correlation coefficient is given to determine the coupling efficiency between the TAA source and extrema eigenmodes. By using a source with a high correlation coefficient, these extrema bulk states are selectively excited consistent with their eigenfields. Furthermore, three control cases are shown that multiple extrema points are simultaneously excited, in order to confirm the validity of the correlation coefficient. Finally, a potential application of a beam-steering device is proposed through selective excitation of ternary extrema. This work develops binary valley states into ternary mix states, rendering more degrees of freedom for on-chip optical information transport, particularly for beam steering and mode division multiplexing.

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Multiband Photonic Topological Valley‐Hall Edge Modes and Second‐Order Corner States in Square Lattices

Kim

2021

Advanced Optical Materials

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inversion symmetry, local Chern invariants have the values of ±1/2 at around K and K' valleys, leading to the existence of valley-locked edge states at the boundaries between two valley-Hall insulators with valley-Chern numbers of opposite signs at K (K') valleys [20,21] . Due to the robustness of the edge states against the structural disorder and the feasibility of fabricating such structures, valley-Hall photonic topological insulators have found promising applications for beam splitting, [31] topological lasing, [32][33][34][35] and frequency conversion. [36] Although the various hexagonal photonic lattices have been revealed to exhibit valley-Hall topological effects, such effects have been rarely investigated in square lattices, since they have non-zero Berry curvatures at non-symmetric points in the first Brillouin zone.Recently, higher-order topological insulating phases have emerged as an important research topic in topological physics, including topological photonics [37][38][39][40][41] and phononics. [42] When a parameter of a photonic topological insulator is changed, gapless edge bands are open above a certain value. For further parameter change, gapped edge states appear accompanying with corner or hinge states, which have dimensions lower than the edge states. As an example, the 2D second-order topological insulators generate zero-dimensional corner states as well as 1D edge states immune to the structural defects, enabling robust photonic nanocavities [43] and nanolasers. [44] In photonic practices, one needs multiband edge and corner states, in particular for nonlinear topological photo nics which frequently requires operating over wide spectral ranges. Up to date, multiband edge states [45,46] in photonic topological systems and their applications for nonlinear optical frequency conversion [36] have been reported, while multiband corner states have still not been investigated. In this work, we reveal 2D photonic crystals with square lattices of triangular dielectric rods to exhibit multiband edge and corner states depending on the structural parameters. For small constituent dielectric rods, there exist gapless multiband edge states immune to the structural disorder. With increasing their sizes, multiple photonic bandgaps appear, resulting in simultaneous occurrence of multiband edge and corner states. By evaluating the eigenstates and their excitation characteristics, we show that the multiband corner states are robust against structural defects. The results presented in this work can find important applications for nonlinear topological frequency conversion.

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Topological Valley Transport in Two-dimensional Honeycomb Photonic Crystals

Cited by 77 publications

References 40 publications

Acoustic graphene network loaded with Helmholtz resonators: a first-principle modeling, Dirac cones, edge and interface waves

Acoustic graphene network loaded with Helmholtz resonators: a first-principle modeling, Dirac cones, edge and interface waves

Selective Excitation of Band Extrema in Valley Photonic Crystals

Multiband Photonic Topological Valley‐Hall Edge Modes and Second‐Order Corner States in Square Lattices

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