Interactions Remove the Quantization of the Chiral Photocurrent at Weyl Points

The chiral photocurrent or circular photogalvanic effect (CPGE) is a\nphotocurrent that depends on the sense of circular polarization. In a\ndisorder-free, noninteracting chiral Weyl semimetal, the magnitude of the\neffect is approximately quantized with a material-independent quantum $e^3/h^2$\nfor reasons of band topology. We study the first-order corrections due to the\nCoulomb and Hubbard interactions in a continuum model of a Weyl semimetal in\nwhich known corrections from other bands are absent. We find that the inclusion\nof interactions generically breaks the quantization. The corrections are\nsimilar but larger in magnitude than previously studied interaction corrections\nto the (nontopological) linear optical conductivity of graphene, and have a\npotentially observable frequency dependence. We conclude that, unlike the\nquantum Hall effect in gapped phases or the chiral anomaly in field theories,\nthe quantization of the CPGE in Weyl semimetals is not protected but has\nperturbative corrections in interaction strength.\n