Laser-driven anisotropic and nonlinear Rashba spin splitting in GaAs monolayer

We investigate the electronic properties of the buckled honeycomb GaAs monolayer under a periodically circularly polarized laser (CPL) by first-principles calculations and Floquet theory. Under the irradiation of CPL with propagation direction in the xy plane, a remarkable Rashba spin splitting (RSS) is induced in the valence and conduction bands at Gamma point. The laser-driven RSS deviates from the classical linear Rashba model in a wide range of wave vectors, and can be interpreted by a nonlinear model involving the third-order terms. The phase diagram of Rashba effect with laser amplitude and propagation direction is worked out. The anisotropy of the nonlinear RSS is mainly determined by the laser propagation direction, providing the possibility of controlling the Rashba anisotropy characteristics. By carefully choosing the laser frequency and amplitude, giant anisotropic RSS can be obtained, which allows the generation of spin-polarized electrons via doping and facilitates the flexibility of spintronic devices.