  Ultrafast optical control of ferroelectricity using intense terahertz fields
has attracted significant interest. Here we show that the nonlinear
interactions between two optical phonons in SnTe, a two-dimensional in-plane
ferroelectric material, enables a dynamical amplification of the electric
polarization within subpicoseconds time domain. Our first principles time
dependent simulations show that the infrared-active out-of-plane phonon mode,
pumped to nonlinear regimes, spontaneously generates in-plane motions, leading
to rectified oscillations in the in-plane electric polarization. We suggest
that this dynamical control of ferroelectric material, by nonlinear phonon
excitation, can be utilized to achieve ultrafast control of the photovoltaic or
other non-linear optical responses.

Materials Science