Fig. 3: Topological surface in the xy plane.
From: Acoustic analogues of three-dimensional topological insulators
a Projected bandstructures in the kxy plane with a hard boundary condition, where the red lines represent surface states. The inset shows the surface Brillouin zone. b 3D view of the simulated surface Dirac cone. Here, kx and ky have units of 4π/9 cm−1. c Experimentally measured iso-frequency slices with Bloch momenta for the surface states. The colour scale represents the acoustic energy density. The dashed lines are drawn to guide the eye. d Measured transmission spectra for the top (red) and bottom (blue) surfaces along the \(\tilde \Gamma \tilde K\) direction, where the colour scale represents the energy density. e A slice of the simulated acoustic pressure distribution with acoustic source excited at both top and bottom surfaces at a frequency of 5.8 kHz, where the colour scale represents the acoustic pressure.
