Observation of nonlinear topological corner states originating from different spectral charges

Abstract

Higher-order topological insulators (HOTIs) are unique topological materials supporting edge states with the dimensionality at least by two lower than the dimensionality of the underlying structure. HOTIs were observed on lattices with different symmetries, but only in geometries, where truncation of HOTI produces a finite structure with the same order of discrete rotational symmetry as that of the unit cell, thereby setting the geometry of insulator edge. Here we experimentally demonstrate a new type of two-dimensional (2D) HOTI based on the Kekule-patterned lattice, whose order of discrete rotational symmetry differs from that of the unit cells of the constituent honeycomb lattice, with hybrid boundaries that help to produce all three possible corners that support effectively 0D corner states of topological origin, especially the one associated with spectral charge 5/6. We also show that linear corner states give rise to rich families of stable hybrid nonlinear corner states bifurcating from them in the presence of focusing nonlinearity of the material. Such new types of nonlinear corner states are observed in hybrid HOTI inscribed in transparent nonlinear dielectric using fs-laser writing technique. Our results complete the class of HOTIs and open the way to observation of topological states with new internal structure and symmetry.

arXiv comment21 pages, 6 figures

References in corpus (55)

• Topological Insulators
• Topological insulators and superconductors
• Topological Photonics
• Topological Photonics
• Photonic Floquet Topological Insulators
• Quantized Electric Multipole Insulators
• Scheme to Achieve Silicon Topological Photonics
• Higher-Order Topological Insulators
• Electric Multipole Moments, Topological Multipole Moment Pumping, and Chiral Hinge States in Crystalline Insulators
• $(d-2)$-dimensional edge states of rotation symmetry protected topological states
• Observation of a phononic quadrupole topological insulator
• Higher-order topological insulators and semimetals on the breathing Kagome and pyrochlore lattices
• Demonstration of a quantized microwave quadrupole insulator with topologically protected corner states
• Quantization of fractional corner charge in $C_n$-symmetric higher-order topological crystalline insulators
• Peculiar Width Dependence of the Electronic Property of Carbon Nanoribbons
• Visualization of higher-order topological insulating phases in two-dimensional dielectric photonic crystals
• Nonlinear topological photonics
• Direct observation of corner states in second-order topological photonic crystal slabs
• Topological protection of photonic mid-gap cavity modes
• Exciton-polariton topological insulator
• Observation of photonic anomalous Floquet Topological Insulators
• Classical higher-order topological insulators
• Quantum memories: emerging applications and recent advances
• Observation of Photonic Topological Valley-Hall Edge States
• Experimental observation of anomalous topological edge modes in a slowly-driven photonic lattice
• Observation of novel edge states in photonic graphene
• Edge Solitons in Nonlinear Photonic Topological Insulators
• Observation of Topological Band Gap Solitons
• Metallic Graphene Nanodisks
• Experimental discovery of bulk-disclination correspondence
• Active topological photonics
• Low-threshold topological nanolasers based on second-order corner state
• Nonlinearity-induced photonic topological insulator
• Nonlinear second-order photonic topological insulators
• Lasing from multipole topological corner states
• A fractional corner anomaly reveals higher-order topology
• Third-harmonic generation in photonic topological metasurfaces
• Topological Materials Discovery from Crystal Symmetry
• Non-linear second-order topological insulators
• Observation of an acoustic octupole topological insulator
• Demonstration of a quantized acoustic octupole topological insulator
• Fractional disclination charge in two-dimensional $C_n-$symmetric topological crystalline insulators
• Nontrivial coupling of light into a defect: the interplay of nonlinearity and topology
• Bimorphic Floquet Topological Insulators
• Tight-binding methods for general longitudinally driven photonic lattices -- edge states and solitons
• Vector Topological Edge Solitons in Floquet Insulators
• Theory of Topological Corner State Laser in Kagome Waveguide Arrays
• Observation of nonlinear disclination states
• Photonic realization of a generic type of graphene edge states exhibiting topological flat band
• Observation of $\pi$ solitons in oscillating waveguide arrays
• Observation of nonlinear fractal higher-order topological insulator
• Light bullets in Su-Schrieffer-Heeger photonic topological insulators
• Optical quantum memory on macroscopic coherence
• Dimers and discrete breathers in Bose-Einstein condensates in a quasi-periodic potential
• Quantum Hall valley Ferromagnets as a platform for topologically protected quantum memory

Cited by in corpus (5)

• Thresholdless corner vortex solitons in fractal Sierpiński topological insulators
• Vortex solitons in disclination quasicrystals
• Nonlinear quadrupole topological insulators
• Stable vortex soliton arrays in disclination-fractal systems
• Self-Accelerating Topological Edge States