Photoinduced spin Chern number change in a two-dimensional quantum spin Hall insulator with broken spin rotational symmetry

We propose a scheme by which the spin Chern number of two-dimensional insulators with generic spin-orbit interaction can be externally controlled by optical methods. When submitting the system to a circularly polarized laser field, and then adiabatically sweeping the amplitude of the latter, the various hopping integrals associated with an electron system effectively turn into tunable variables. This in turn transforms the spin Chern number, which governs the topological properties of the system into a function of the laser amplitude. This scheme can steer a conventional insulator into the quantum spin Hall state, and vice versa. We anticipate that our findings, which provide a firmly grounded connection between optical techniques and spin transport, will open up the possibility of developing spintronics devices that build on the physics of the photosteering of spin currents.