Fig. 3: Gapped topological edge states induced by anomalous quadrupole in the second band gap. | Nature Communications

Fig. 3: Gapped topological edge states induced by anomalous quadrupole in the second band gap.

From: Symmetry-protected hierarchy of anomalous multipole topological band gaps in nonsymmorphic metacrystals

Fig. 3: Gapped topological edge states induced by anomalous quadrupole in the second band gap.

a Measured (hot color) and calculated (green) dispersions of the acoustic edge states. Gray curves represent calculated acoustic bulk bands. b, c Top: measured and simulated acoustic pressure profiles of the edge states launched by a point-like source (indicated by the red stars), respectively. Below: photo of the fabricated sample and the illustration of the structure, respectively. Inset in b: photo of a unit-cell. d Acoustic pressure profiles for the two edge states marked by the red and blue dots in a, with phase, amplitude and Poynting vectors (blue arrows) shown near the edge. Phase vortex centers and phase winding directions are marked by the black dots and arrows, respectively. The edge is formed between the sonic crystal and the hard-wall boundary made of photosensitive resin. Unit-cell geometry parameters are the same as that in Fig. 1.

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