Photomodulated edge states and multiterminal transport in silicenelike nanoribbons

Abstract

We study the band structures and time-averaged transport properties of the Floquet systems irradiated by variously polarized monochromatic light theoretically based on the Floquet-Green's function method. It reveals that the circularly polarized light can generate the anisotropic chiral edge modes and the polarization of light further manipulates these modes by altering their spatial distributions and spin orientations. Benefitting from external electric and exchange fields, the valley polarizations and band gaps can be induced to implement a variety of exotic photo-dressed topological phases. Furthermore, the circularly polarized light modifies the spin-resolved dc conductance remarkably, giving rise to a highly spin-polarized transport in the bulk band-gap regime. The short-range disorder manifests itself by forming a conductance arc symmetrically with respect to zero energy as well as a half-integer quantized conductance plateau in the two-terminal Floquet devices. The transverse dc conductance in T-shape devices is sensitive to the polarization of light; namely, the left-circularly polarized light minimizes the transverse conductance while the right-handed one greatly enhances it by inverting the moving directions of the edge modes. The strong correlation between the spin and light polarizations offers us a feasible tool to either realize devices in spintronic or detect the polarization of monochromatic light by simple transport measurements.