Circular and magnetoinduced photocurrents in Weyl semimetals

We develop a theory of the direct interband and indirect intraband\nphotogalvanic effects in Weyl semimetals belonging to the gyrotropic classes\nwith improper symmetry operations. At zero magnetic field, an excitation of\nsuch a material with circularly polarized light leads to a photocurrent whose\ndirection depends on the light helicity. We show that in the semimetals of the\nC$_{2v}$ symmetry, an allowance for the tilt term in the effective Hamiltonian\nis enough to prevent cancellation of the photocurrent contributions from the\nWeyl cones of opposite chiralities. In the case of the C$_{4v}$ symmetry, in\naddition to the tilt it is necessary to include terms of the second- or\nthird-order in the electron quasi-momentum. For indirect intraband transitions,\nthe helicity-dependent photocurrent generated within each Weyl node takes on a\nuniversal value determined by the fundamental constants, the light frequency\nand electric field. We have complementarily investigated the magneto-gyrotropic\nphotogalvanic effect, i.e. an appearance of a photocurrent under unpolarized\nexcitation in a magnetic field. In quantized magnetic fields, the photocurrent\nis caused by optical transitions between the one-dimensional magnetic subbands.\nA value of the photocurrent is particularly high if one of the photocarriers is\nexcited to the chiral subband with the energy below the cyclotron energy.\n