Topology of Weyl semimetal interfaces uncovered by reflection shift

The reflection point is different from the incident point on the interface between two Weyl semimetals, and a spatial shift happens during the reflection. The reflection shift vector as a function of in-plane wave vector shows vortex structures in the incident pocket (the projection of the isoenergy surface on the junction interface) and on the pocket edge. We propose a topological quantity, which is defined by the contour integration of reflection shift along the pocket edge and is proven to be the number of edge vortices as well as that of the interface Fermi arcs connected to the pocket. Every vortex is an interface particle loaded with unit topological charge and the distribution of these topological particles reflects the internal structure of the incident pocket under the influence of the transmitted medium.