Higher-order Weyl semimetals
摘要：Higher-order topology yields intriguing multidimensional topological phenomena, while Weyl semimetals have unconventional properties such as chiral anomaly. However, so far, Weyl physics remain disconnected with higher-order topology. Here, we report the theoretical discovery of higher-order Weyl semimetals and thereby the establishment of such an important connection. We demonstrate that higher-order Weyl semimetals can emerge in chiral materials such as chiral tetragonal crystals as the intermediate phase between the conventional Weyl semimetal and 3D higher-order topological phases. Higher-order Weyl semimetals manifest themselves uniquely by exhibiting concurrent chiral Fermi-arc surface states, topological hinge states, and the momentum-dependent fractional hinge charge, revealing a novel class of higher-order topological phases. We then present experimental realization of higher-order Weyl points in chiral phononic crystals with screw symmetry. We observe the Weyl points in the bulk, the Fermi arcs on the surface and the hinge states connecting the higher-order Weyl points on the hinges of a finite-sized phononic crystal.