Photoinduced Topological Phase Transition and Optical Conductivity of Black Phosphorene

We theoretically study the photoinduced topological phase transition of black phosphorene induced by laser light with moderate-intensity, which can satisfy the experimentally realistic requirement to preserve the quality of the sample. By deriving the effective Floquet Hamiltonian in terms of pseudo-spin S=1/2 degrees of freedom, we calculate the Chern number and the optical conductivity of the system with varying laser frequency. As one can expect from the photon-assisted transport, the longitudinal optical conductivity has a threshold frequency at Ω=△/h with △ being the band gap of black phosphorene. Unlike the longitudinal optical conductivity, the optical Hall conductivity sharply increases when hΩ goes beyond one half of the band gap △/2. We also show that the Chern number changes from trivial to non-trivial one upon increasing frequency beyond hΩ=△/2.