Fig. 2
From: Topological sound
Analogue quantum spin Hall effect in sonic crystals. The construction of doubly degenerate Dirac-like cones based on a zone folding and b accidental degeneracy is presented. c The spin-locked edge state propagation and d its robustness against various defects. Wave propagation in a regular waveguide is also presented as comparison. Panels c, d are adapted from ref. 43
