Surface Linear Photogalvanic Response in Magnetic Weyl Semimetal Co₃Sn₂S₂

Co₃Sn₂S₂ is a magnetic Weyl semimetal that preserves inversion symmetry in the bulk. Its surface, however, breaks this symmetry, enabling photogalvanic effects arising purely from the surface. Using a diagrammatic perturbation framework, we compute the second-order linear photogalvanic effect (LPGE) based on a tight-binding model for few-layer Co₃Sn₂S₂. Interestingly, the effect can be reversed by reversing the net ferromagnetic moment of the material, allowing the system to function as a magnetically controlled photo-switch. In the process, we clarify how calculating surface response functions in Weyl semimetals using tight-binding models differs from general response calculations, which should aid similar calculations in other systems.