Non-linear response functions and disorder: the case of the photo galvanic effect

The circular photogalvanic effect (CPGE) is a non-linear photocurrent which is generated in materials with broken inversion symmetry when they are shed with circularly polarised light. In Weyl semi-metals, the CPGE is quantized in terms of fundamental constants and the Chern numbers associated with the Weyl nodes. In this work, we investigate the effect of pointlike disorder onto the quantization of CPGE. Implementing 1st-order and self-consistent Born approximations, we identify that the quantization of CPGE is broken and perturbative corrections in the scattering strength emerge, which we further classify in terms of self-energy and vertex corrections.