Acoustic higher-order topological insulator on a kagome lattice

By Haoran Xue, Yahui Yang, Fei Gao, Y. Chong, Baile Zhang. Nature Materials, 2018

785 citations recorded by the source corpus.

Higher-order topological insulators1–5 are a family of recently predicted topological phases of matter that obey an extended topological bulk–boundary correspondence principle. For example, a two-dimensional (2D) second-order topological insulator does not exhibit gapless one-dimensional (1D) topological edge states, like a standard 2D topological insulator, but instead has topologically protected zero-dimensional (0D) corner states. The first prediction of a second-order topological insulator1, based on quantized quadrupole polarization, was demonstrated in classical mechanical6 and electromagnetic7,8 metamaterials. Here we experimentally realize a second-order topological insulator in an acoustic metamaterial, based on a ‘breathing’ kagome lattice9 that has zero quadrupole polarization but a non-trivial bulk topology characterized by quantized Wannier centres2,9,10. Unlike previous higher-order topological insulator realizations, the corner states depend not only on the bulk topology but also on the corner shape; we show experimentally that they exist at acute-angled corners of the kagome lattice, but not at obtuse-angled corners. This shape dependence allows corner states to act as topologically protected but reconfigurable local resonances.A second-order topological insulator in an acoustical metamaterial with a breathing kagome lattice, supporting one-dimensional edge states and zero-dimensional corner states is demonstrated.

Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics

View Paper: https://www.semanticscholar.org/paper/5faa92a95a5b3d97aac1fe57d21ddd75d01b63c2

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Citations in the corpus

Quantization of fractional corner charge in Cn -symmetric higher-order topological crystalline insulators (2018, background): “[24] Haoran Xue, Yahui Yang, Fei Gao, Yidong Chong, and Baile Zhang, “Acoustic higher-order topological insulator on a kagome lattice,” arXiv:1806.”
Higher-order non-Hermitian skin effect (2020, background): “Higher-order topology was observed in various experiments [20–28], and may lead to unique phenomena and functionalities due to its boundary physics.”
Quantum states and intertwining phases in kagome materials (2023, background): “For example, corner states in a 2D artificial breathing kagome lattice have been detected in acoustic systems and photonic waveguides among others 65–67 .”
Corner states of light in photonic waveguides (2018, background): “The first experimental realisations of such higher-order boundary modes have very recently been achieved: the quadrupole topological insulator [11] has been realised in topolectric circuits [19], mechanical metamaterials [20], and microwave circuits [21] while corner modes predicted to appear in bre”
Topological acoustics (2022, background): “which was experimentally implemented in acoustics with coupled-resonator lattices [90, 91] (Fig.”