Vortex-enhanced photovoltaic current in disordered topological semimetals (Part 2)

In disordered topological semimetals, real-space crystalline defects interplay with momentum-space wave function singularities to enhance the bulk photovoltaic current. What's singular is the interband Berry phase, or equivalently the phase of the optical dipole matrix element, which has a vortex structure in momentum space. Such optical vortices are topologically guaranteed to exist in all topological semimetals. For such semimetals which are noncentrosymmetric, electron-impurity scattering mediates a bulk photovoltaic current which is enhanced by the presence of optical vortices. This is part 2 of a 2-part talk.