Photoinduced transition between conventional and topological insulators in two-dimensional electronic systems

Manipulating the topological properties of insulators, encoded in invariants such as the Chern number and its generalizations, is now a major issue for realizing novel charge/spin responses in electron systems. We propose that a simple optical means --subjecting to a driving laser field with circular polarization, can be fruitfully incorporated to this end. Taking as a prototypical example the two-band insulator first considered by Haldane, we show how the electron system can be tuned through phases associated with different Chern numbers as the laser intensity is adiabatically swept; i.e., a photo-induced analog of the quantum Hall plateau transition. The implications of our findings includes the possibility of laser-tuning a conventional insulator into a quantum spin Hall system.