  We demonstrate the injection of pure valley-orbit currents in multi-valley
semiconductors and present the theory of this effect. We studied photo-induced
transport in $n$-doped (111)-oriented silicon metal-oxide-semiconductor field
effect transistors at room temperature. By shining circularly polarized light
on exact oriented structures with six equivalent valleys, non-zero electron
fluxes within each valley are generated, which compensate each other and do not
yield a net electric current. By disturbing the balance between the valley
fluxes, in this work by applying linearly polarized radiation as well as by
introducing a nonequivalence of the valleys by disorientation, we approve that
the pure valley currents can be converted into a measurable electric current.
