Topological valley-chiral edge states of Lamb waves in elastic thin plates

Abstract

We investigate the nontrivial topology of the band structure of Lamb waves in a thin phononic crystal plate. When inversion symmetry is broken, a valley pseudospin degree of freedom is formed around K and K′ valleys for the A0 Lamb mode, which is decoupled from the S0 and SH0 modes in the low-frequency regime. Chiral edge states are explicitly demonstrated, which are immune to defects and exhibit unidirectional transport behaviors when intervalley scattering is weak. The quantum valley Hall effect is thus simulated in a simple way in the context of Lamb waves.