Figure 5. Surface states of Co₂TiGe(010).

(a) The first BZ and (010) surface of Co₂TiGe. (b) The Fermi surface of Co₂TiGe(010), which is derived by a simulation in the absence of SOC. The orange line indicates the projected nodal line on the surface. (c) Energy dispersion along the path illustrated by the white line in panel (b). (d,e) Constant energy contours of Co₂TiX(010) at the energy of of Weyl points , , respectively, which are produced by the simulation by considering SOC. The projected Weyl nodes are indicated by black and white balls. The projected bulk band pockets are connected with each other, making the surface states indistinguishable. (f) E-k dispersion along the red circles in (d). (g) A cartoon demonstrating the ideal Weyl cones and Fermi arc, which can both be easily discerned. (h) A cartoon showing a realistic case. If a projected bulk band covers the projected Weyl nodes on surface, the Fermi arc merges with the bulk pockets and becomes unobservable. Consequently, the Chern number of the topological 2D manifold can not be identified by the number of chiral surface states.