Figure 1. Nontrivial band structure and Berry curvature of a topological semimetal.

(a) A schematic of the energy spectrum of a topological semimetal. (k_x, k_y, k_z) is the wave vector. . (b) The vector plot of the Berry curvature in momentum space. The conduction and valence bands of a topological semimetal touch at the Weyl nodes, at which a pair of monopoles is hosted. The arrows show that the flux of the Berry curvature flows from one monopole (red) to the other (blue), defining the nontrivial topological properties of a topological semimetal.