Optically Controlled Valleytronics in Floquet-Dirac Systems

We propose to create valleytronic devices by shaping the valley electronic states in a two dimensional Dirac material, such as graphene or molybdenum disulfide, with circularly polarized lasers. By mixing and tuning the optical parameters of the lasers appropriately, the non-equilibrium steady state of electrons in different valleys can be differentiated to have unequal gaps. In particular, one valley can be tuned to be gapless while the other is gapped, thus creating regions in which the conductance is strongly valley-dependent. This valley-polarized conductance is protected against moderate impurity disorder and small deviations in optical parameters. Thus, our proposed method provides a novel way of engineering robust electronic states with light.