Figure 4: Topologically trivial and nontrivial edge modes facing a one-dimensional random potential.
From: Topologically protected elastic waves in phononic metamaterials
(a) Trivial crystal is designed using the crystal in Fig. 1 with the triangular holes rotated by 12.5° clockwise (grey region) and anticlockwise (blue region). To create the bandgap in the same spectral range as in the nontrivial case, the structure is scaled up by factor of 1.07% in all geometrical parameters. In this structure with mirror symmetry, the symmetric mode is excited. (b) The nontrivial crystal is exactly the same as in Fig. 3c. The excitation frequency in both panels is 130.5 kHz.
