We develop a theoretic description of the photogalvanic current induced by a high frequency radiation in asymmetric nanostructures and show that it describes well the results of numerical simulations. Our studies allow to understand the origin of the electronic ratchet transport in such systems and show that they can be used for creation of new types of detectors operating at room temperature in a terahertz radiation range.PACS. 72.40.+w Photoconduction and photovoltaic effects -73.63.-b Electronic transport in nanoscale materials and structures -05.45.Ac Low-dimensional chaos

We show that the optical excitation of graphene with polarized light leads to the pure valley current where carriers in the valleys counterflow. The current in each valley originates from asymmetry of optical transitions and electron scattering by impurities owing to the warping of electron energy spectrum. The valley current has strong polarization dependence, its direction is opposite for normally incident beams of orthogonal linear polarizations. In undoped graphene on a substrate with high susceptibility, electron-electron scattering leads to an additional contribution to the valley current that can dominate.Comment: 4+ pages, 2 figure

Abstract. Spin-orbit (SO) interaction of electrons confined near the curved semiconductor surface is studied. The curvature of surface determines the new mechanism of SO interaction which complements the known mechanisms occurring in planar systems. The specific cases of nanosphere and nanotube are considered.