Fig. 2: Realization of the acoustic non-Hermitian valley filter.
From: Lossy phononic metamaterials for valley nonreciprocity
a Photograph of the sample. Inset: Enlarged view of the domain B with coupling loss, where the yellow shadow marks a unit cell. The designed loss is achieved by the holes on the waveguides sealed with the sound-absorbing sponges. b Schematic of the acoustic unit cell. Green circles represent the holes on the waveguide. c Simulated complex bulk band dispersions near the K valley. d Simulated projected dispersions of a ribbon with periodic boundary conditions in the x direction. e Simulated pressure field distribution at 5.86 \({{{\rm{kHz}}}}\) for the ABA sandwich-shaped structure, which is excited by ten point-sources (blue stars) on the left boundary. f Top panel: Measured spatial Fourier spectra of the acoustic field within the green rectangles at the input (left) and output (right) ports of \({{{\rm{ABA}}}}\), respectively. Bottom panel: The corresponding simulated results.
