  We theoretically demonstrate that 100\% valley-polarized transport in
monolayers of MoS$_{2}$ and other group-VI dichalcogenides can be obtained
using off-resonant circularly polarized light. By tuning the intensity of the
off-resonant light the intrinsic band gap in one valley is reduced, while it is
enhanced in the other valley, enabling single valley quantum transport. As a
consequence, we predict (i) enhancement of the longitudinal electrical
conductivity, accompanied by an increase in the spin-polarization of the
flowing electrons, (ii) enhancement of the intrinsic spin Hall effect, together
with a reduction of the intrinsic valley Hall effect, and (iii) enhancement of
the orbital magnetic moment and orbital magnetization. These mechanisms provide
appealing opportunities to the design of nanoelectronics based on
dichalcogenides.
