Higher-order topological semimetal in acoustic crystals

The notion of higher-order topological insulators has endowed materials with states beyond the first order. Particularly, a three-dimensional (3D) insulator can host topologically protected 1D hinge states, referred to as second-order insulator, or 0D corner third-order insulator. Similarly, 3D semimetal be envisaged if it hosts on hinges. Here we report realization Weyl in 3D-printed acoustic crystal, which possesses points momentum space, 2D Fermi arc surfaces and gapless Like surface also connect projections points. Our experimental results evidence existence semimetal, may pave way towards innovative devices. A based exhibiting points, been experimentally demonstrated.