Photocurrent in gyrotropic Weyl semimetals

Photocurrents in the Weyl semimetals belonging to the gyrotropic symmetry classes have been theoretically studied. It has been shown that the circular photocurrent transverse to the direction of light incidence appears in weakly gyrotropic crystals with the C$_{nv}$ ($n = 3,4,6$) symmetry only when spin-dependent terms both linear and quadratic or cubic in the quasimomentum, as well as a spin-independent term resulting in the tilt of the cone dispersion, are taken into account in the electron effective Hamiltonian. A polarization-independent magnetic-field-induced photocurrent, which is allowed only in gyrotropic systems, has been predicted. For crystals with the $C_{2v}$ symmetry, a microscopic mechanism of the photocurrent in a quantized magnetic field, which is generated in direct optical transitions between the ground and first excited magnetic subbands, has been considered. It has been shown that this photocurrent becomes nonzero in the presence of the anisotropic tilt of dispersion cones.