• Photonics Research
  • Vol. 12, Issue 10, 2078 (2024)
Hua Zhong1, Yaroslav V. Kartashov2, Yongdong Li1, Ming Li3, and Yiqi Zhang1,*
Author Affiliations
  • 1Key Laboratory for Physical Electronics and Devices, Ministry of Education, School of Electronic Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, China
  • 2Institute of Spectroscopy, Russian Academy of Sciences, Moscow 108840, Russia
  • 3State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics of Chinese Academy of Sciences, Xi’an 710119, China
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    DOI: 10.1364/PRJ.524824 Cite this Article Set citation alerts
    Hua Zhong, Yaroslav V. Kartashov, Yongdong Li, Ming Li, Yiqi Zhang, "Topological edge states in a photonic Floquet insulator with unpaired Dirac cones," Photonics Res. 12, 2078 (2024) Copy Citation Text show less

    Abstract

    Topological insulators are most frequently constructed using lattices with specific degeneracies in their linear spectra, such as Dirac points. For a broad class of lattices, such as honeycomb ones, these points and associated Dirac cones generally appear in non-equivalent pairs. Simultaneous breakup of the time-reversal and inversion symmetry in systems based on such lattices may result in the formation of the unpaired Dirac cones in bulk spectrum, but the existence of topologically protected edge states in such structures remains an open problem. Here a photonic Floquet insulator on a honeycomb lattice with unpaired Dirac cones in its spectrum is introduced that can support unidirectional edge states appearing at the edge between two regions with opposite sublattice detuning. Topological properties of this system are characterized by the nonzero valley Chern number. Remarkably, edge states in this system can circumvent sharp corners without inter-valley scattering even though there is no total forbidden gap in the spectrum. Our results reveal unusual interplay between two different physical mechanisms of creation of topological edge states based on simultaneous breakup of different symmetries of the system.
    iψz=12(2x2+2y2)ψR(x,y,z)ψ,

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    R=m,npm,nexp((xxm,n(z))2+(yym,n(z))2d2).

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    bϕ=12(2x2+2y2)ϕ+R(x,y,z)ϕ+iϕz,

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    U(k,Z)=Zexp(i0ZH(k,z)dz)=exp(iHeff(k)Z),

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    H(k,z)=t[PP].

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    Bn(k)=inn(un|kxHeff|unun|kyHeff|un(bnbn)2un|kyHeff|unun|kxHeff|un(bnbn)2),

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    Cv,n=12πvBv,n(k)dk,

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    FK(k)={1,|kK|rk,0,other places,

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    Hua Zhong, Yaroslav V. Kartashov, Yongdong Li, Ming Li, Yiqi Zhang, "Topological edge states in a photonic Floquet insulator with unpaired Dirac cones," Photonics Res. 12, 2078 (2024)
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