Circular photogalvanic effect in interacting Weyl semimetals

The circular photogalvanic effect (CPGE) is a photocurrent that depends on the sense of circular polarization. In a disorder-free, non-interacting chiral Weyl semimetal, the magnitude of the effect is approximately quantized with a material-independent quantum e^3/h^2 for reasons of band topology. We study the first-order corrections due to the Coulomb and Hubbard interactions in a continuum model of the Weyl points. We find that the inclusion of interactions generically breaks the quantization yet the corrections are non-divergent. The corrections are similar in spirit to the case of interaction corrections to the (non-topological) linear conductivity of graphene. Thus, we conclude that, unlike the quantum Hall effect or the chiral anomaly in field theories, the quantization of the CPGE is not protected but has perturbative corrections in interaction strength.