Light-induced topological phases in two-dimensional gapped Dirac materials

We present a comparative study of light-induced topological phases in two-dimensional massive Dirac models with and without quadratic corrections, which depicts different inversion symmetry-breaking Dirac materials. We find that a light has two effects on the Floquet band topology: it not only inverts the massive bands near the Dirac points but also introduces pseudospin-orbital coupling around the resonant points of light-matter interaction. Depending on the presence or absence of the quadratic corrections, the interplay of these two effects of light results in versatile topological phases with dissipationless valley polarized edge currents. In particular, without quadratic correction as exemplified by gapped graphene, a circularly polarized light induces a pair of in-gap edge states at each valley, which propagate on the same direction at a fixed boundary. A linearly polarized light also induces a pair of in-gap edge states, while propagating on the opposite direction at a fixed boundary. When including the quadratic correction as exemplified by monolayer transition-metal dichalcogenides, a circularly polarized light can induce two pairs of in-gap edge states located at a single valley, while a linearly polarized light does not induce any in-gap edge state. These edge currents as controlled by switching on/off the applied light and its polarization nature suggest an optical way to engineer valleytronic devices.