Intrinsic triple degeneracy point bounded by nodal surfaces in chiral photonic crystal

Abstract

In periodic systems, band degeneracies are usually protected and classified by spatial symmetries. However, the Gamma point at zero-frequency of a photonic system is an intrinsic degeneracy due to the polarization degree of freedom of electromagnetic waves. We show here that in chiral photonic crystals, such an intrinsic degeneracy node carries +(-)2 chiral topological charge and the topological characters is the same as a spin-1 Weyl point manifested as a triple degeneracy of two linear propagating bands intersecting a flat band representing the electrostatic solution. Such an intrinsic triple degeneracy point (TDP) at Gamma is usually buried in bulk band projections and the topological charge at photonic zero-frequency has never been observed. Here, by imposing space-group screw symmetry to the chiral photonic crystal, the Brillouin zone boundary is transformed into an oppositely charged nodal surface enclosing the Gamma point. The emergent Fermi-arcs on sample surface are then forced to connect the bulk band projections of these topological singularities, revealing the embedded non-trivial topology.

References in corpus (51)

• Topological Insulators
• Topological insulators and superconductors
• Electronic Structure of Pyrochlore Iridates: From Topological Dirac Metal to Mott Insulator
• Topological Photonics
• Photonic Floquet Topological Insulators
• Photonic Analogue of Two-dimensional Topological Insulators and Helical One-Way Edge Transport in Bi-Anisotropic Metamaterials
• Topological quantum chemistry
• Robust optical delay lines via topological protection
• Beyond Dirac and Weyl fermions: Unconventional quasiparticles in conventional crystals
• Experimental observation of Weyl points
• Symmetry-based Indicators of Band Topology in the 230 Space Groups
• Weyl points and line nodes in gapless gyroid photonic crystals
• The space group classification of topological band insulators
• Topological classification of crystalline insulators through band structure combinatorics
• Geometrodynamics of Spinning Light
• Topological negative refraction of surface acoustic waves in a Weyl phononic crystal
• Multiple types of topological fermions in transition metal silicides
• Hourglass Fermions
• Large Fermi Arcs in Unconventional Weyl Semimetal RhSi
• A new type of Weyl semimetal with quadratic double Weyl fermions in SrSi2
• Discovery of topological chiral crystals with helicoid arc states
• New classes of chiral topological nodes with non-contractible surface Fermi arcs in CoSi
• Photonic Topological Anderson Insulators
• Nodal surface semimetals: Theory and material realization
• Double-Weyl phonons in transition-metal monosilicides
• Topological Photonic Phase in Chiral Hyperbolic Metamaterials
• Observation of Chiral Fermions with a Large Topological Charge and and Associated Fermi-Arc Surface States in CoSi
• Node-Surface and Node-Line Fermions From Nonsymmorphic Lattice Symmetries
• Chiral Topological Semimetal with Multifold Band Crossings and Long Fermi arcs
• Towards Three-Dimensional Weyl-SurfaceSemimetals in Graphene Networks
• Observation of Double Weyl Phonons in Parity-Breaking FeSi
• Plasmon Weyl Degeneracies in Magnetized Plasma
• Hyperbolic Weyl point in reciprocal chiral metamaterial
• Filling-Enforced Gaplessness in Band Structures of the 230 Space Groups
• Topological triply-degenerate point with double Fermi arcs
• Discovery of coexisting Dirac and triply degenerate magnons in a three-dimensional antiferromagnet
• Mode-Locked Topological Insulator Laser Utilizing Synthetic Dimensions
• Ideal Unconventional Weyl Point in a Chiral Photonic Metamaterial
• Observation of quadratic Weyl points and double-helicoid arcs
• Emergent pseudospin-1 Maxwell fermions with a threefold degeneracy in optical lattices
• Photonic Dirac monopoles and skyrmions: spin-1 quantization
• Topological Triply Degenerate Points Induced by Spin-Tensor-Momentum Couplings
• Room temperature electrically pumped topological insulator lasers
• Space-group theory of photonic bands
• Observation of a singular Weyl point surrounded by charged nodal walls in PtGa
• Geometrically protected triple-point crossings in an optical lattice
• Location and topology of the fundamental gap in photonic crystals
• Acoustic spin-1 Weyl semimetal
• Experimental demonstration of non-adjacent band topology connecting multiple nodal links
• Photonic nodal lines with quadrupole Berry curvature distribution
• Spin-1 Weyl Point and Surface Arc State in a Chiral Phononic Crystal