Figure 3: Chern numbers from Berry flux.

Topological 2D surface obtained from mapping each point in the BZ to a 3D d(k) vector when hz takes the values (a) −3hc/2, (b) −hc/2, (c) hc/2 and (d) 3hc/2. The arrows in the figure emanate from the origin, which acts as a monopole of Berry flux.