Role of Shift Vector in High-Harmonic Generation from Noncentrosymmetric Topological Insulators under Strong Laser Fields

As a promising avenue to obtain new extreme ultraviolet light source and detect electronic properties, high-harmonic generation (HHG) has been actively developed in both theory experiment. In solids lacking inversion symmetry, when electrons undergo nonadiabatic transition, directional charge shift occurs is characterized by vector, which measures the real-space of photoexcited electron hole. For first time, we have revealed that vector plays prominent roles tunneling mechanism three-step model for under strong laser fields. Since determined topological properties related wave functions, expect HHG with its contribution can provide direct knowledge on band topology noncentrosymmetric insulators (TIs). Kane-Mele realistic material BiTeI, found reverses happens during phase transition between normal insulators. Under oscillating fields, reversal leads completely opposite radiation time high-order harmonics. This makes feasible all-optical strong-field method directly identify non-centrosymmetric TIs.