Giant bulk photovoltaic effect and spontaneous polarization of single-layer monochalcogenides

We implement and use a first-principles density functional theory approach to calculate the shift current response of monolayer group-IV monochalcogenides. We find a larger effective three- dimensional effective polarization (\textasciitilde 1.9 C/m2) and shift current (\textasciitilde 200 $\mu $A/V2) than have been previously observed in common ferroelectrics. By using a one-dimensional Rice-Mele tight-binding model we investigate the shift-current tensor along the polarization axis, its relation with polarization, and the conditions under which shift-current reaches a maximum [1]. Importantly, our calculations predict that shift current can be largest in the UV visible range, indicating the potential of these materials for optoelectronic applications.[1] arXiv:1610.06589