Momentum and Real-Space Study of Topological Semimetals and Topological Defects

We draw a phenomenological analogy between the topological defect of a screw dislocation and the electronic Weyl semimetal topology class including their bulk and surface manifestations. In the bulk, both can be assigned a chirality which can be calculated from the crystallographic curvature of the screw dislocation or the Berry curvature of the Weyl bands. On the surface, the chiral screw dislocations give rise to open-contour surface modes in the form of a crystallographic step edge uniquely emanating from the screw termination. The bulk Weyl nodes induce surface Fermi-arc states that uniquely terminate at the surface projection of the bulk Weyl node. We use scanning tunneling microscopy to visualize the surface manifestation of both topological structures. The surface topology of the screw dislocation is visualized in the surface topography. The surface momentum-space topology of the Weyl semimetal is visualized and characterized spectroscopically using quasi-particle interference.