Photoinduced topological phase transition in black phosphorous and graphene

Recent advances in ultrafast spectroscopy open a route toward engineering new phase of solids with optical pumping. The nonequilibrium electronic states of solids driven by a strong AC electromagnetic field manifest many topological states different from equilibrium ones. Using first-principles calculations and Floquet theorem, we studied the dressed states of black phosphorous and graphene under periodic driven of laser. Intriguing photo-dressed electronic states including Floquet Dirac semimetals, Floquet topological insulators etc can be engineered in black phosphorous by changing the direction, intensity and frequency of incident laser. The coexistence of type-I and type-II Floquet Dirac fermion can be realized spontaneously, which can be monitored by simulating the pump-probe time and angular-resolved photoelectron spectroscopy. Our works demonstrate the Floquet engineering of ultrafast changing the topological properties of solids. 1. Hang Liu et al., arxiv: 1710.05546.