Synthetic Weyl points with various planar symmetries in phononic crystals

Abstract

We present a study on the existence of synthetic Weyl points with various planar symmetries in phononic crystals. We design a set of phononic crystals to display Weyl points at high-symmetry points with different symmetries in both square and honeycomb lattices. We demonstrate that, in a square lattice, double Weyl points are protected by C4 rotation symmetry, while in a honeycomb lattice, they are protected by C3 rotation symmetry. Additionally, we investigated the effects of symmetry on double Weyl points. The results indicate that double Weyl points would split into two single Weyl points along high-symmetry lines if we break the corresponding symmetries. The distributions of Weyl points in various symmetries are presented systematically. Finally, gapless surface states and the robust one-way acoustic transport in a square lattice are demonstrated in a double Weyl system.