Topological spin-Hall edge states of flexura wave in perforated metamaterial plates

This paper investigates the pseudo-spin based edge states for flexural waves in a honeycomb perforated phononic plate, which behaves as an elastic analogue of the quantum spin Hall effect. We utilize the finite element method to analyse the dispersion for flexural waves based on Mindlin's plate theory. Topological transition takes place around a double Dirac cone at Gamma point by adjusting the sizes of perforated holes. We develop an effective Hamiltonian to describe the bands around the two doubly degenerated states and analyse the topological invariants. This leads us to further observe the topologically protected edge states, localized at the interface between two lattices. We demonstrate the unidirectional propagation of the edge waves along topological interface, as well as their robustness against defects and sharp bends.