We propose theoretically (Phys. Rev. Lett. 125, 146401 (2020) web link) and observe experimentally higher-order Weyl semimetals. The experiment is achieved via a home-designed sonic crystal. The main feature of higher-order Weyl semimetal is the coexistence of Fermi arc surface states and the hinge-arc states connecting the higher-order Weyl points.

Nature Materials 20, 794–799 (2021)

Link to the paper: https://www.nature.com/articles/s41563-021-00985-6