Strong photogalvanic effect in Weyl materials due to magnetic resonances

We study the photogalvanic effect in Weyl semimetals under a magnetic field, focusing on the shift current. Using the Kubo formalism for an ideal, clean Weyl node at zero temperature, we derive a general analytical expression valid for arbitrary light frequency, Fermi energy, and magnetic field strength. We identify a series of resonances that can be probed experimentally. To complement the microscopic analysis, we employ the semiclassical Boltzmann approach, which allows us to incorporate finite scattering phenomenologically. Unlike most previous studies using this method, we do not treat the magnetic field perturbatively; instead, we solve the Boltzmann equation for a Weyl node exactly within the limits of validity of the semiclassical theory. Our solution reproduces the low-frequency resonances and elucidates the role of finite scattering.