Observation of nonlinear disclination states

Abstract

Introduction of controllable deformations into periodic materials that lead to disclinations in their structure opens novel routes for construction of higher-order topological insulators hosting topological states at disclinations. Appearance of these topological states is consistent with the bulk-disclination correspondence principle, and is due to the filling anomaly that results in fractional charges to the boundary unit cells. So far, topological disclination states were observed only in the linear regime, while the interplay between nonlinearity and topology in the systems with disclinations has been never studied experimentally. We report here bon the experimental observation of the nonlinear photonic disclination states in waveguide arrays with pentagonal or heptagonal disclination cores inscribed in transparent optical medium using the fs-laser writing technique. The transition between nontopological and topological phases in such structures is controlled by the Kekulé distortion coefficient $r$ with topological phase hosting simultaneously disclination states at the inner disclination core and spatially separated from them corner, zero-energy, and extended edge states at the outer edge of the structure. We show that the robust nonlinear disclination states bifurcate from their linear counterparts and that location of their propagation constants in the gap and, hence, their spatial localization can be controlled by their power. Nonlinear disclination states can be efficiently excited by Gaussian input beams, but only if they are focused into the waveguides belonging to the disclination core, where such topological states reside.

11 pages, 6 figures

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Cited by in corpus (16)

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• Tutorial: Classifying Photonic Topology Using the Spectral Localizer and Numerical $K$-Theory
• Probing topology in nonlinear topological materials using numerical $K$-theory
• Observation of nonlinear topological corner states originating from different spectral charges
• Topological edge states in photonic Floquet insulator with unpaired Dirac cones
• Topological solitons in coupled Su-Schrieffer-Heeger waveguide arrays
• Observation of nonlinear higher-order topological insulators with unconventional boundary truncations
• Two-dimensional flat-band solitons in superhoneycomb lattices
• Polariton Topological Insulators with Disclinations
• Thresholdless corner vortex solitons in fractal Sierpiński topological insulators
• Vortex solitons in disclination quasicrystals
• Quadratic solitons in higher-order topological insulators
• Floquet states on disclinations
• Topological linear and nonlinear gap modes in defected dimer lattice with fourth-order diffraction
• Stable vortex soliton arrays in disclination-fractal systems
• Self-Accelerating Topological Edge States