Observation of squeezed Chern insulator in an acoustic fractal lattice

Abstract

Topological insulators are a new phase of matter with the distinctive characteristics of an insulating bulk and conducting edge states. Recent theories indicate there even exist topological edge states in the fractal-dimensional lattices, which are fundamentally different from the current studies that rely on the integer dimensions. Here, we propose and experimentally demonstrate the squeezed Chern insulator in a fractal-dimensional acoustic lattice. First, through calculating the topological invariant of our topological fractal system, we find the topological phase diagram is squeezed by about 0.54 times, compared with that of the original Haldane model. Then by introducing synthetic gauge flux into an acoustic fractal lattice, we experimentally observe the one-way edge states that are protected by a robust mobility gap within the squeezed topological regimes. Our work demonstrates the first example of acoustic topological fractal insulators and provides new directions for the advanced control of sound waves.

References in corpus (19)

• Quantized Anomalous Hall Effect in Magnetic Topological Insulators
• Photonic Analogue of Two-dimensional Topological Insulators and Helical One-Way Edge Transport in Bi-Anisotropic Metamaterials
• Reflection-Free One-Way Edge Modes in a Gyromagnetic Photonic Crystal
• Topological Acoustics
• Observation of phononic helical edge states in a mechanical 'topological insulator'
• Observation of topological valley transport of sound in sonic crystals
• Classical higher-order topological insulators
• Non-Hermitian Topological Sensors
• Acoustic realization of quadrupole topological insulators
• Disorder-induced Floquet Topological Insulators
• Realization of an acoustic third-order topological insulator
• Experimental observation of non-Abelian topological charges and bulk-edge correspondence
• Observation of non-Abelian topological semimetals and their phase transitions
• Observation of a phononic higher-order Weyl semimetal
• Photonic Floquet topological insulators in a fractal lattice
• Higher-order Dirac sonic crystals
• Observation of Non-Abelian Thouless Pump
• Bosonic Bott Index and Disorder-Induced Topological Transitions of Magnons
• Topological Random Fractals

Cited by in corpus (9)

• Observation of nonlinear fractal higher-order topological insulator
• Haldane model on the Sierpiński gasket
• Non-Hermitian Quantum Fractals
• Corner and Edge States in Topological Sierpinski Carpet Systems
• Wave functions in the Critical Phase: a Planar \textit{Sierpiński} Fractal Lattice
• Topological Phases in Fractals: Local Spin Chern Marker in the Sierpinski carpet Kane-Mele-Rashba Model
• Orbital magnetization in Sierpinski fractals
• Bose-Einstein condensation in exotic lattice geometries
• Resonant helical multi-edge transport in Sierpiński carpets