Observation of a phononic quadrupole topological insulator

By Marc Serra-Garcia, Valerio Peri, Roman Susstrunk, Osama R. Bilal, T. Larsen, L. Villanueva, Sebastian D. Huber. Nature, 2017

901 citations recorded by the source corpus.

The modern theory of charge polarization in solids is based on a generalization of Berry’s phase. The possibility of the quantization of this phase arising from parallel transport in momentum space is essential to our understanding of systems with topological band structures. Although based on the concept of charge polarization, this same theory can also be used to characterize the Bloch bands of neutral bosonic systems such as photonic or phononic crystals. The theory of this quantized polarization has recently been extended from the dipole moment to higher multipole moments. In particular, a two-dimensional quantized quadrupole insulator is predicted to have gapped yet topological one-dimensional edge modes, which stabilize zero-dimensional in-gap corner states. However, such a state of matter has not previously been observed experimentally. Here we report measurements of a phononic quadrupole topological insulator. We experimentally characterize the bulk, edge and corner physics of a mechanical metamaterial (a material with tailored mechanical properties) and find the predicted gapped edge and in-gap corner states. We corroborate our findings by comparing the mechanical properties of a topologically non-trivial system to samples in other phases that are predicted by the quadrupole theory. These topological corner states are an important stepping stone to the experimental realization of topologically protected wave guides in higher dimensions, and thereby open up a new path for the design of metamaterials.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/88dbc36d7ab66ce99514be111021d76a0d9feec2

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In Atomic and Molecular Physics, and Optics

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Citations in the corpus

Quantization of fractional corner charge in Cn -symmetric higher-order topological crystalline insulators (2018, background): “[75] Marc Serra-Garcia, Valerio Peri, Roman Süsstrunk, Osama R.”
Tailoring Structure‐Borne Sound through Bandgap Engineering in Phononic Crystals and Metamaterials: A Comprehensive Review (2022, methodology): “[298] via an elegantly designed hopping mechanism in a perturbative”